[3.14] Document that returning `sys.monitoring.DISABLE` in response to a global event raises `ValueError` (GH-140726) (GH-141014)

Document that returning `sys.monitoring.DISABLE` in response to a global event raises `ValueError` (GH-140726)
(cherry picked from commit 8a7dbb7a68b5da1f3f1805f564c028f1eea4ebc3)

Co-authored-by: Brett Cannon <brett@python.org>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>