fix: trigger Maven deploy from release-please via workflow_dispatch (#1981)

## Summary

- Events created by `GITHUB_TOKEN` don't trigger other workflows,
  so the tag push and `release: published` events from release-please
  never triggered the deploy workflow
- Replace `push: tags` / `release: published` triggers on `release.yml`
  with `workflow_dispatch`
- Have release-please call `gh workflow run release.yml` after creating
  a release
- Also serves as a manual fallback (`gh workflow run release.yml --ref
v1.5.1`)

## Test plan

- [ ] CI passes
- [ ] After merge, manually dispatch deploy for v1.5.1
- [ ] On next release, deploy triggers automatically from release-please

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

.github/workflows/release-please.yml

@@ -7,6 +7,7 @@ on:
       - main
 
 permissions:
+  actions: write
   contents: write
   issues: write
   pull-requests: write
@@ -22,3 +23,11 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           config-file: .github/config/release-please-config.json
           manifest-file: .github/config/.release-please-manifest.json
+
+      - name: Trigger deploy to Maven Central
+        if: ${{ steps.release-please.outputs.releases_created == 'true' }}
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: >
+          gh workflow run release.yml
+          --ref ${{ steps.release-please.outputs.tag_name }}

.github/workflows/release.yml

@@ -2,12 +2,7 @@
 name: Deploy to Maven Central
 
 on:
-  push:
-    tags:
-      - "v*.*.*"
-  release:
-    types:
-      - published
+  workflow_dispatch: {}
 
 jobs:
   deploy: