enable invoke dynamic on JRuby by default

@headius told me that the only known issues are when jruby is being
called directly from java and in a container. Seeing we aren't doing
that, we can enable this.

lib/language_pack/ruby.rb

@@ -159,7 +159,7 @@ def default_java_opts
   # default JRUBY_OPTS
   # return [String] string of JRUBY_OPTS
   def default_jruby_opts
-    "-Xcompile.invokedynamic=false"
+    "-Xcompile.invokedynamic=true"
   end
 
   # list the available valid ruby versions