envutil.rb: use keyword argument

* test/ruby/envutil.rb (assert_valid_syntax): use keyword argument.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46389 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-06-10

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46390 b2dd03c8-39d4-4d8f-98ff-823fe69b080e