docs: admin-guide: update tiny script for number of taint flags

docs: admin-guide: update tiny script for number of taint flags

Account for 2 new taint flags being added by increasing the number of
bits handled by the tiny show-tainted-flags example script.

Fixes: 8eea4e744758 ("taint: Add TAINT_FWCTL")
Fixes: 2852ca7fba9f ("panic: Taint kernel if tests are run")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260216063729.2832770-1-rdunlap@infradead.org>