Suppress Ruby experimental features warning messages

The Remote Development codebase uses Ruby's experimental pattern
matching syntax
(https://docs.ruby-lang.org/en/3.0/syntax/pattern_matching_rdoc.html).
As a result, booting `gitlab-rails console` shows a stream of these
warnings at compile-time:

```
warning: One-line pattern matching is experimental, and the behavior
may change in future versions of Ruby!
```

Let's just squelch these warnings for now since they're development
warnings, and CI should catch issues if this breaks.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/420811

Changelog: fixed

Author: stanhu

config/templates/gitlab-rails/bundle_exec_wrapper.erb

@@ -40,4 +40,7 @@ else
   privilege_drop="-u ${gitlab_user}:${gitlab_group}"
 fi
 
-exec <%= install_dir %>/embedded/bin/chpst -e <%= install_dir %>/etc/gitlab-rails/env ${privilege_drop} -U ${gitlab_user}:${gitlab_group} <%= install_dir %>/embedded/bin/bundle exec <%= command %>
+# Suppress one-line pattern matching warnings: https://gitlab.com/gitlab-org/gitlab/-/issues/420811
+rubyopt="RUBYOPT=-W:no-experimental"
+
+exec <%= install_dir %>/embedded/bin/chpst -e <%= install_dir %>/etc/gitlab-rails/env ${privilege_drop} -U ${gitlab_user}:${gitlab_group} /usr/bin/env ${rubyopt} <%= install_dir %>/embedded/bin/bundle exec <%= command %>