Unable to install and enable plugins from helm chart

I installed apisix successfully helm chart with ArgoCd application.

I then tried to add the "limit-count" plugin, but when I open the dashboard I don't see this plugin.

I can add this plugin manually.

This is the Apisix application yaml I used:

```
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
name: loadbalancer-apisix
namespace: argocd
annotations:
argocd.argoproj.io/sync-wave: "1"
finalizers:
- resources-finalizer.argocd.argoproj.io
spec:
destination:
namespace: api-gw
server: https://kubernetes.default.svc
project: default
source:
chart: apisix
repoURL: https://charts.apiseven.com
targetRevision: v2.1.0
helm:
releaseName: apisix
values: |
service:
type: LoadBalancer
annotations:
service.beta.kubernetes.io/aws-load-balancer-internal: "true"
service.beta.kubernetes.io/aws-load-balancer-type: "nlb"
service.beta.kubernetes.io/aws-load-balancer-backend-protocol: tls
service.beta.kubernetes.io/aws-load-balancer-additional-resource-tags: Environment=dev
ingress-controller:
enabled: "true"
config:
apisix:
serviceNamespace: "api-gw"
adminAPIVersion: v3

plugins: ["limit-count"]

pluginAttrs: {
"limit-count": {
"count": 2,
"time_window": 60,
"rejected_code": 503,
"key": "remote_addr",
"policy": "redis",
"redis_host": "apisix-redis-master.default.svc.cluster.local",
"redis_port": 6379,
"redis_password": "my_pass",
"redis_database": 1,
"redis_timeout": 1001
}
}

dashboard:
enabled: "true"
syncPolicy:
automated: {}
syncOptions:
- CreateNamespace=true
```

Any idea why it didn't work? (I don't think it has anything to do with argocd - it just a normal helm installation).

------------
I also tried to edit the configmap to enable the plugin, but it didn't work also:

```
apiVersion: v1
kind: ConfigMap
metadata:
name: apisix-configmap
namespace: api-gw
data:
config.yaml: |
plugins:
limit-count:
enable: true
config:
count: 100
```

Start by rendering chart v2.1.0 with the supplied values and inspect the generated APISIX ConfigMap and pod configuration, then compare them with the dashboard's plugin list. Verify whether plugins and pluginAttrs are accepted at those chart keys; done means the rendered config enables limit-count and the dashboard shows it after an upgrade.

Written by the indexing model from the issue text.