Bump cbrgm/mastodon-github-action from 2.1.5 to 2.1.8

Bumps [cbrgm/mastodon-github-action](https://github.com/cbrgm/mastodon-github-action) from 2.1.5 to 2.1.8.
- [Release notes](https://github.com/cbrgm/mastodon-github-action/releases)
- [Commits](cbrgm/mastodon-github-action@v2.1.5...v2.1.8)

---
updated-dependencies:
- dependency-name: cbrgm/mastodon-github-action
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/release_notifications.yml

@@ -83,7 +83,7 @@ jobs:
     steps:
       - name: Send Mastodon Notification
         id: mastodon
-        uses: cbrgm/mastodon-github-action@v2.1.5
+        uses: cbrgm/mastodon-github-action@v2.1.8
         with:
           access-token: ${{ secrets.MASTODON_ACCESS_TOKEN }}
           url: ${{ secrets.MASTODON_URL }}

.github/workflows/release_notifications_manual_tests.yml

@@ -102,7 +102,7 @@ jobs:
     steps:
       - name: Mastodon Notification
         id: mastodon
-        uses: cbrgm/mastodon-github-action@v2.1.5
+        uses: cbrgm/mastodon-github-action@v2.1.8
         with:
           access-token: ${{ secrets.MASTODON_ACCESS_TOKEN }} # access token
           url: ${{ secrets.MASTODON_URL }} # https://example.social