[3.12] gh-110938: Fix error messages for indented blocks with functio… (#110990)

[3.12] gh-110938: Fix error messages for indented blocks with functions and classes with generic type parameters (GH-110973)
(cherry picked from commit 24e4ec7766fd471deb5b7e5087f0e7dba8576cfb)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>