[rubygems/rubygems] Removed to workaround for Bundler 2.2.

The current oldest support Ruby version is 3.2. And Ruby 3.2 bundled
Bundler 2.5. It means RG 4.0 can drop to support Bundler 2.2.

ruby/rubygems@592ac09b5c

Author: hsbt

lib/rubygems/installer.rb

@@ -67,23 +67,6 @@ class Gem::Installer
   attr_reader :package
 
   class << self
-    #
-    # Changes in rubygems to lazily loading `rubygems/command` (in order to
-    # lazily load `optparse` as a side effect) affect bundler's custom installer
-    # which uses `Gem::Command` without requiring it (up until bundler 2.2.29).
-    # This hook is to compensate for that missing require.
-    #
-    # TODO: Remove when rubygems no longer supports running on bundler older
-    # than 2.2.29.
-
-    def inherited(klass)
-      if klass.name == "Bundler::RubyGemsGemInstaller"
-        require "rubygems/command"
-      end
-
-      super(klass)
-    end
-
     ##
     # Overrides the executable format.
     #