feat: using the current version of the announcement bot for Mastodon (#333)

This version strip away commit links and keeps issue links without Markdown syntax
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated the release announcement workflow to use a newer version of
the Mastodon posting action.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: cmeesters

.github/workflows/announce-release.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Post to Mastodon
-        uses: snakemake/mastodon-release-post-action@v1.5.0
+        uses: snakemake/mastodon-release-post-action@main # == latest
         with:
           access-token: ${{ secrets.MASTODONBOT }}
           pr-title: ${{ github.event.head_commit.message }}