Remove GAP3 package #19164
Description
The GAP3 package (#8906) contains binaries instead of installing from source. This is not acceptable.
This branch reverts the merge of #8906, as it would have brought binary executables from an external source into Sage.
sage-devel thread: https://groups.google.com/d/topic/sage-devel/EhW0nKGoKHU/discussion
CC: @sagetrac-sage-combinat @nthiery @saliola @stumpc5
Component: packages: optional
Keywords: GAP3
Author: Dima Pasechnik
Branch/Commit: 35ee338
Reviewer: Travis Scrimshaw, Jeroen Demeyer
Issue created by migration from https://trac.sagemath.org/ticket/19164