fix(templates/kubit): logic inversion on kubitSingleNamespace

Prior to this PR setting `Values.kubitSingleNamespace` to `false` would
cause it to watch only a single namespace, which seems to be the `kubit`
namespace itself. The reason it ends up watching the `kubit` namespace
can be seen in the deployment's namespace setting:

```
  namespace: {{if .Values.kubitSingleNamespace}}{{.Values.namespaceOverride | default .Release.Namespace}}{{else}}kubit{{end}}
```

charts/influxdb3-clustered/templates/kubit.yml

@@ -79,7 +79,7 @@ spec:
     spec:
       containers:
       - env:
-{{- if not .Values.kubitSingleNamespace}}
+{{- if .Values.kubitSingleNamespace}}
         - name: KUBIT_WATCHED_NAMESPACE
           valueFrom:
             fieldRef:
@@ -118,4 +118,4 @@ spec:
           type: RuntimeDefault
       serviceAccountName: kubit
       terminationGracePeriodSeconds: 10
-  {{end}}
+  {{end}}