building docker container fails

*Summary*

Executing the `docker-build.sh` from the release package yields a `/root/support-diagnostics-8.1.4/docker-build.sh: line 2: cd: ../docker: No such file or directory` error.

The error can be traced back to the `docker-buid.sh` file. In line 2, there is a cd statement which only makes sense in the folder hierarchy of the github project.

https://github.com/elastic/support-diagnostics/blob/1d90e4cb905f3c124b47065d41d1c1677bfab127/scripts/docker-build.sh#L2-L3

When using the [latest release file 8.1.4](https://github.com/elastic/support-diagnostics/releases/tag/v8.1.4) the `docker-build.sh` file is directly in the root directory.

```
[root@host support-diagnostics-8.1.4]# pwd
/root/support-diagnostics-8.1.4
[root@host support-diagnostics-8.1.4]# ls -1
config
diagnostics.bat
diagnostics.sh
docker
docker-build.sh
export-monitoring.bat
export-monitoring.sh
import-monitoring.bat
import-monitoring.sh
lib
scrub.bat
scrub.sh
```

*Solution*
Put the `docker-build.sh` file in the same location in the github repo and in the release package.