all: change absolute wiki links to relative Change-Id: I534ed3b8f45a69ff388ba4d081916bc5c77559dd Reviewed-on: https://go-review.googlesource.com/c/wiki/+/595815 Auto-Submit: Ian Lance Taylor <iant@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Commit-Queue: Ian Lance Taylor <iant@golang.org>