Remove 'run' method name check in module node

The check for whether a method is being declared named 'run' that was added to ModuleNode when merging GROOVY-6585 is incorrect.  

I wish you had discussed any issues you had with me on the pull request before merging it.  I spent a lot of time the last several days on this and checked exactly this case carefully, including adding such a check, backing it off from an error to a warning, and then removing the warning since this is a lint issue not a compiler issue.