Drop unneeded require memoization

Author: bpo

lib/thor/line_editor/readline.rb

@@ -2,8 +2,8 @@ class Thor
   module LineEditor
     class Readline < Basic
       def self.available?
-        @readline_reqd ||= begin
-            require "readline"
+        begin
+          require "readline"
         rescue LoadError
         end
 

spec/line_editor/readline_spec.rb

@@ -2,7 +2,7 @@
 
 describe Thor::LineEditor::Readline do
   before do
-    # Eagerly check Readline availability and cache for this spec
+    # Eagerly check Readline availability before mocking
     Thor::LineEditor::Readline.available?
     unless defined? ::Readline
       ::Readline = double("Readline")