test: remove typed-ast from test-requirements.txt

It fails to build with recent Python plus it is also no longer
maintained; the recommendation is to use the standard library
ast module instead, as per https://pypi.org/project/typed-ast/

Signed-off-by: Sergio Correia <scorreia@redhat.com>

test-requirements.txt

@@ -3,7 +3,6 @@ dbus-python
 setuptools
 # packages required for mypy
 sqlalchemy-stubs
-typed-ast
 types-python-dateutil
 types-PyYAML
 types-redis