Update gitter-realtime-client (no removing entries on snapshot, only add/merge)

Thanks to @viktomas for the gitter-realtime-client update!

Update gitter-realtime-client (no removing entries on snapshot, only add/merge)

• MR with changes: https://gitlab.com/gitlab-org/gitter/realtime-client/-/merge_requests/26
• Release issue: https://gitlab.com/gitlab-org/gitter/realtime-client/-/issues/23

Dev notes

Test if GulpUglifyError: unable to minify JavaScript is happening locally:

npm run gulp -- package assemble --skip-stage validate --skip-stage test