gdb: Remove the webcore.py pretty printer.
https://bugs.webkit.org/show_bug.cgi?id=117992

Reviewed by Jochen Eisinger.

webcore.py has been only a placeholder for backwards compatibility
for almost 3 years. It should be safe enough to remove it now.

* gdb/webcore.py: Removed.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@151987 268f45cc-cd09-0410-ab3c-d52691b4dbfc