gem rdoc gem_name fails with undefined method 'force=' for an instance of RDoc::RubygemsHook

[tompng]

Found in Reline's CI failure https://github.com/ruby/reline/actions/runs/12330703999
Failed jobs are irb [2.7..3.3 and head] ubuntu latest

Reproduction:

$ docker run --rm -ti rubylang/rubyfarm
root@bacda24563ca:/# ruby -v
ruby 3.4.0dev (2024-12-15T13:36:38Z master 366fd9642f) +PRISM [x86_64-linux]
root@bacda24563ca:/# gem rdoc readline
ERROR:  While executing gem ... (NoMethodError)
    undefined method 'force=' for an instance of RDoc::RubygemsHook

      doc.force = options[:overwrite]
         ^^^^^^^^
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/commands/rdoc_command.rb:80:in 'block in Gem::Commands::RdocCommand#execute'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/commands/rdoc_command.rb:77:in 'Array#each'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/commands/rdoc_command.rb:77:in 'Gem::Commands::RdocCommand#execute'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/command.rb:326:in 'Gem::Command#invoke_with_build_args'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/command_manager.rb:253:in 'Gem::CommandManager#invoke_command'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/command_manager.rb:194:in 'Gem::CommandManager#process_args'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/command_manager.rb:152:in 'Gem::CommandManager#run'
	/opt/ruby/lib/ruby/3.4.0+1/rubygems/gem_runner.rb:57:in 'Gem::GemRunner#run'
	/opt/ruby/bin/gem:12:in '<main>'

RDoc::Ruby"G"emsHook have method force= but RDoc::Ruby"g"emsHook used by rubygems does not have it.

[st0012]

I think this is related to #1171. cc @hsbt @mterada1228

IMO, RubygemsHook should delegate all previously supported methods to RubyGemsHook to achieve real compatibility support. I'll open a PR later.