pidgin: fix --without-gui

The options apparently need to be above the dependencies otherwise the dependencies kick in first. 

Should deal with [this comment](https://github.com/Homebrew/homebrew/commit/7537f3663d0ca35e5848d0a9644ebc86c92d267f#commitcomment-9000071).
Might want to add another `deprecated_option` here to migrate it to `without-x11` (or is that different)?