kcsan: Fix trivial typo in Kconfig help comments

Fix trivial typo in Kconfig help comments in KCSAN_SKIP_WATCH and
KCSAN_SKIP_WATCH_RANDOMIZE

Signed-off-by: Ryosuke Yasuoka <ryasuoka@redhat.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>