devel/rubygem-prometheus-client-mmap: update to 0.25.0

Required for gitlab-ce 16.1

Reported upstream that 0.26.0 will not work with gitlab 16.1:
https://gitlab.com/gitlab-org/gitlab/-/issues/416848

Changelog:
https://gitlab.com/gitlab-org/ruby/gems/prometheus-client-mmap/-/blob/master/CHANGELOG.md#v0250
(cherry picked from commit 42358c305176194df0fb9db49d1e6c86cd771450)