fix callable enum narrowing

[EmmanuelNiyonshuti]

Fixes ##17222

Narrowing an enum to a literal(with == or match) gives a LiteralType, which was not being checked when type checking a call. This PR add a LiteralType branch to check_call that will delegate to its fallback instance.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

scipy (https://github.com/scipy/scipy)
- scipy/conftest.py:678: error: "Literal['skip']" not callable  [misc]
+ scipy/conftest.py:678: error: "str" not callable  [operator]
- scipy/conftest.py:678: error: "Literal['xfail']" not callable  [misc]