[3.11] gh-106107: document correct error that's raised when a mutable default value for a field is detected (gh-106109) (gh-106116)

gh-106107: document correct error that's raised when a mutable default value for a field is detected (gh-106109)
(cherry picked from commit 512f299e557f4ab60768d36cee9968bd92116367)

Co-authored-by: Roderich Schupp <roderich.schupp@gmail.com>