[doc] Fix typo in what's new in 3.10 (GH-26911) (GH-26940)

The `try` statement was missing a colon and therefore was not exemplifying the correct `SyntaxError`.
(cherry picked from commit dcb1caef5bd8e90e1ecb4c07d7114e51b49fe37a)

Co-authored-by: Rodrigo Girão Serrão <rodrigogiraoserrao@gmail.com>
1 file changed