Attempt to fix bool re-narrowing

[sobolevn]

Let's see what mypy_primer and CI will say.

Closes#11839
Refs #10389

[sobolevn]

For some reason all builds with mypyc-compiled mypy fail. While regular tests pass. No idea why.

[sobolevn]

Ok, I will try something else.

[github-actions]

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

graphql-core (https://github.com/graphql-python/graphql-core)
+ tests/type/test_definition.py:1115: error: Argument 1 to "isnan" has incompatible type "None"; expected "Union[SupportsFloat, SupportsIndex]"+ tests/language/test_visitor.py:73: error: Value of type "Node" is not indexable
zulip (https://github.com/zulip/zulip)
+ zerver/lib/events.py:495: error: Statement is unreachable [unreachable]+ zerver/lib/events.py:513: error: Statement is unreachable [unreachable]+ zerver/lib/events.py:534: error: Statement is unreachable [unreachable]+ zerver/lib/events.py:600: error: Statement is unreachable [unreachable]+ zerver/tests/test_events.py:495: error: Statement is unreachable [unreachable]
core (https://github.com/home-assistant/core)
- homeassistant/config_entries.py:474: error: Returning Any from function declared to return "bool" [no-any-return]

[sobolevn]

See #11839 (comment)