Fix softprops/action-gh-release source from master (default) to release branch. (#368)

Author: olivier-roussel

.github/workflows/ci.yml

@@ -223,6 +223,7 @@ jobs:
           name: ${{ env.RELEASE_NAME }}
           tag_name: ${{ env.RELEASE_TAGNAME }}
           fail_on_unmatched_files: false
+          target_commitish: ${{ env.RELEASE_NAME }}
           body: |
             Last updated on ${{ env.RELEASE_DATE }}
           files: |