[gdb/testsuite] Remove superfluous -quiet and -ex set width/height 0

INTERNAL_GDBFLAGS contains:
- -quiet
- -iex "set width 0"
- -iex "set height 0"

There are test-cases that add these once more.

Clean this up.

Tested on x86_64-linux.

PR testsuite/31649
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31649