[gdb/testsuite] Don't require gold for gdb.base/morestack.exp

While working on PR26935 I noticed that the test-case requires the gold
linker, but doesn't really need it.

The -fuse-ld=gold was added to support the printf in the test-case, which
prints some information but is not otherwise needed for the test-case.

Fix this by removing the printf and the corresponding -fuse-ld=gold.

Tested on x86_64-linux.

Also checked that the test still fails when the fix from the commit that added
the test-case is reverted.

gdb/testsuite/ChangeLog:

2021-01-04  Tom de Vries  <tdevries@suse.de>

	* gdb.base/morestack.c: Remove printf.
	* gdb.base/morestack.exp: Don't use -fuse-ld=gold.