HelmGitlabRelease: send both versions to master, record mappings table

Update HelmGitlabRelease to send both versions to master. This allows manage_versions script to insert the entry into version mapping documentation on master as well.

The previous method relied on calling master with only version. Changes were made in the called script to ignore appVersion changes to Chart.yml when on the master branch, but add the entry to the version mapping table in documentation. To do this, we need to send app_version.

Add the resulting changes to version_mappings.md to the items to be committed.

See https://gitlab.com/charts/gitlab/merge_requests/704#note_146534026

Relates to https://gitlab.com/charts/gitlab/issues/999

cc @twk3