gimp: drop dependency on webkitgtk2.
gimp: drop dependency on webkitgtk2.

This was only used for the Help Browser, but we didn't even install the docs.

necrophcodr/void-packages,coredumb/void-packages,coredumb/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,coredumb/void-packages,coredumb/void-packages,coredumb/void-packages,coredumb/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages