[bundler/bundler] Remove unnecessary method parameter

https://github.com/bundler/bundler/commit/72194d1aac

lib/bundler/templates/Executable.bundler

@@ -75,10 +75,10 @@ m = Module.new do
   def load_bundler!
     ENV["BUNDLE_GEMFILE"] ||= gemfile
 
-    activate_bundler(bundler_requirement)
+    activate_bundler
   end
 
-  def activate_bundler(bundler_requirement)
+  def activate_bundler
     gem_error = activation_error_handling do
       gem "bundler", bundler_requirement
     end