[rubygems/rubygems] Fix "did you mean" suggestions for unknown commands

Since Ruby 3.4.5, which ships with did_you_mean-2.0.0, RubyGems no
longer gives "did you mean" suggestions for unknown commands.

This is because did_you_mean-2.0.0 completely removed the SPELL_CHECKERS
constant, and attaching "did you mean" to `Gem::UnknownCommandError`
errors required this constant to be defined.

The fix is to remove conditions on the `SPELL_CHECKERS` constant.

rubygems/rubygems@9287cd80ed

Author: deivid-rodriguez

lib/rubygems/exceptions.rb

@@ -23,15 +23,8 @@ def initialize(unknown_command)
   def self.attach_correctable
     return if defined?(@attached)
 
-    if defined?(DidYouMean::SPELL_CHECKERS) && defined?(DidYouMean::Correctable)
-      if DidYouMean.respond_to?(:correct_error)
-        DidYouMean.correct_error(Gem::UnknownCommandError, Gem::UnknownCommandSpellChecker)
-      else
-        DidYouMean::SPELL_CHECKERS["Gem::UnknownCommandError"] =
-          Gem::UnknownCommandSpellChecker
-
-        prepend DidYouMean::Correctable
-      end
+    if defined?(DidYouMean) && DidYouMean.respond_to?(:correct_error)
+      DidYouMean.correct_error(Gem::UnknownCommandError, Gem::UnknownCommandSpellChecker)
     end
 
     @attached = true

test/rubygems/test_gem_command_manager.rb

@@ -78,7 +78,7 @@ def test_find_command_unknown_suggestions
 
     message = "Unknown command pish".dup
 
-    if defined?(DidYouMean::SPELL_CHECKERS) && defined?(DidYouMean::Correctable)
+    if defined?(DidYouMean)
       message << "\nDid you mean?  \"push\""
     end