According to https://gitlab.com/gitlab-org/gitlab/-/issues/352957
the variable name `CI_BUILD_REF_NAME` is deprecated since gitlab 9.0
and was finally removed in gitlab 16.0. The new name of this variable
since gitlab 9.0 is `CI_COMMIT_REF_NAME`.

Hence, to keep our branch name matching feature working, we have to adjust
to the renaming.

Warning: This patch simply replaces the variable name. I did not do any
further checks of the script.