www/gitlab: fixed regressions from

9c7ec30e93f9d4bcf7dd7b213b582ac05138e31f
b38ff7a19b6c3dbe3007d1f88d12e600b5a288a8

Could not find compatible versions

Because every version of gitlab-backup-cli depends on bigdecimal ~> 3.1

and bigdecimal >= 3.1, < 4.A could not be found in locally installed gems,
gitlab-backup-cli cannot be used.

So, because Gemfile depends on gitlab-backup-cli >= 0,

version solving has failed.

• Error code 6