Remove dep on typed-ast

This is no longer support in Python 3.13, and no longer required for Python>=3.8

Author: jgraham

tools/requirements_mypy.txt

@@ -2,7 +2,6 @@ mypy==1.14.0
 mypy-extensions==1.0.0
 toml==0.10.2
 tomli==2.0.1
-typed-ast==1.5.5
 types-atomicwrites==1.4.5.1
 types-python-dateutil==2.9.0.20240906
 types-PyYAML==6.0.12.12