Bump robotology/gh-action-nightly-merge from 1.5.0 to 1.5.2

Bumps [robotology/gh-action-nightly-merge](https://github.com/robotology/gh-action-nightly-merge) from 1.5.0 to 1.5.2.
- [Release notes](https://github.com/robotology/gh-action-nightly-merge/releases)
- [Commits](robotology/gh-action-nightly-merge@14b4a4c...81570ba)

---
updated-dependencies:
- dependency-name: robotology/gh-action-nightly-merge
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/stable-merge.yml

@@ -47,7 +47,7 @@ jobs:
         token: ${{ env.INSTALLATION_TOKEN }}
 
     - name: Merge master into dev
-      uses: robotology/gh-action-nightly-merge@14b4a4cf358f7479aa708bee05cf8a794d6a2516 #v1.5.0
+      uses: robotology/gh-action-nightly-merge@81570ba03dd370f582bd3f52d47672d29191829f #v1.5.2
       with:
         stable_branch: 'master'
         development_branch: 'dev'