encoding/xml: skip TestCVE202230633 for short tests

encoding/xml: skip TestCVE202230633 for short tests

TestCVE202230633 uses a bunch of memory, and the input cannot be
feasibly reduced while maintaining the behavior hasn't regressed. This
test could be reasonably removed, but I'd rather keep it around if we
can.

Fixes #53814

Change-Id: Ie8b3f306efd20b2d9c0fb73122c26351a55694c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/417655
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>