Use latest RDoc

The latest RDoc contains ruby/rdoc#1657, which
fixes install-doc failures on some platforms.

Author: st0012

gems/bundled_gems

@@ -37,7 +37,7 @@ ostruct             0.6.3   https://github.com/ruby/ostruct
 pstore              0.2.1   https://github.com/ruby/pstore
 benchmark           0.5.0   https://github.com/ruby/benchmark
 logger              1.7.0   https://github.com/ruby/logger
-rdoc                7.2.0   https://github.com/ruby/rdoc
+rdoc                7.2.0   https://github.com/ruby/rdoc 911b122a587e24f05434dbeb2c3e39cea607e21f
 win32ole            1.9.3   https://github.com/ruby/win32ole
 irb                 1.17.0  https://github.com/ruby/irb
 reline              0.6.3   https://github.com/ruby/reline

lib/bundled_gems.rb

@@ -1,7 +1,7 @@
 # -*- frozen-string-literal: true -*-
 
 # :stopdoc:
-module Gem
+module Gem # :nodoc: TODO: it's a workaround for RDoc's Prism parser handling stopdoc differently, remove me later
 end
 # :startdoc: