Elasticseach and Kibana related warning spam after upgrade to 7.x

If the ElasticSearch has also Kibana installed, after updating ElasticSearch to 7.x Graylog logs are full of spam like this:

```
2020-12-17T12:46:50.780+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:46:50.781+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:46:50.789+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-system-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:46:50.791+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-system-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:47:00.776+02:00 WARN [RestClient] request [GET http://localhost:9200/graylog2_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:47:00.777+02:00 WARN [RestClient] request [GET http://localhost:9200/graylog2_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:47:00.793+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:47:00.799+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:47:00.804+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-system-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]
2020-12-17T12:47:00.805+02:00 WARN [RestClient] request [GET http://localhost:9200/gl-system-events_*/_alias?ignore_throttled=false&ignore_unavailable=false&expand_wildcards=open&allow_no_indices=false] returned 1 warnings: [299 Elasticsearch-7.10.1-1c34507e66d7db1211f66f3513706fdf548736aa "this request accesses aliases with names reserved for system indices: [.kibana_task_manager, .kibana], but in a future major version, directaccess to system indices and their aliases will not be allowed"]

```

As it is only a warning so far this is mostly an annoyance. The real issue is that ElasticSearch 8.x will probably break Graylog if also Kibana is used.