Pin changelogerator to the latest compatible version for the current flow (#4392)

polkadot/.github/workflows/publish-draft-release.yml

@@ -82,7 +82,7 @@ jobs:
           RUSTC_NIGHTLY: ${{ needs.get-rust-versions.outputs.rustc-nightly }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
-          gem install changelogerator git toml
+          gem install changelogerator:0.0.16 git toml
           ruby $GITHUB_WORKSPACE/polkadot/scripts/github/generate_release_text.rb | tee release_text.md
       - name: Create draft release
         id: create-release