Merge pull request #1812 from ksss/rubyvm-yjit-enable

Add optional kwargs of RubyVM::YJIT.enable

core/ruby_vm.rbs

@@ -315,7 +315,7 @@ module RubyVM::YJIT
   # *   `true`: Enable stats. Print stats at exit.
   # *   `:quiet`: Enable stats. Do not print stats at exit.
   #
-  def self.enable: () -> void
+  def self.enable: (?stats: false | true | :quiet) -> void
 
   # <!--
   #   rdoc-file=yjit.rb