docs/system: remove extraneous sentence

Lest we confuse the reader about something we are no longer showing in
the example.

Fixes: 132f8ec799c (target/arm: change default pauth algorithm to impdef)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-id: 20260406165648.997995-1-alex.bennee@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 file changed