Chore: Migrate workflows to use create-github-app-token (#2142)

- Removes dependabot.yml as renovate will update grafana-sdk for us
- Migrates to `create-github-app-token`
- Pin workflows
- Removes is-compatible.yml I found that workflow not helping much but
creating an annoyingly long comment

Fixes https://github.com/grafana/oss-big-tent-squad/issues/144

.github/workflows/compatibility-72.yml

@@ -14,11 +14,11 @@ jobs:
   compatibility-check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           persist-credentials: false
 
-      - uses: actions/setup-go@v5.3.0
+      - uses: actions/setup-go@f111f3307d8850f501ac008e886eec1fd1932a34 # v5.3.0
 
       - name: Start Zabbix environment
         run: |