Add mutex_m & drb Gems for Rails 7.0 and Ruby 3.4

mutex_m and drb are not part of the defaults Gems in
Ruby 3.4 anymore. Since Rails 7.0 and rspec-rails depend
on them, we add it to the local dev Gemfile.

(cherry picked from commit 51ad85b)

Gemfile

@@ -69,3 +69,10 @@ gem "rails_live_reload", "~> 0.3.5"
 gem "dartsass-rails", "~> 0.5.0"
 
 gem "gem-release", "~> 2.2"
+
+if rails_version == "7.0"
+  # Necessary for Rails 7.0 and Ruby 3.4
+  gem "mutex_m", "~> 0.3", require: false
+  # Necessary for Rails 7.0, rspec-rails and Ruby 3.4
+  gem "drb", "~> 2.2", require: false
+end