Incorrect check of runtime_checkable protocol which is not used `@` class decorator

[mixilchenko]

Bug Report

When Protocol is not marked with runtime_checkable decorator, isinstance(instance, runtime_checkable(ProtocolClass)) gives incorrect error.

This could be pretty useful when you don't want to mark protocol as runtime_checkable for the execution while in tests you would like to check protocol compliance

To Reproduce

playground link - https://mypy-play.net/?mypy=master&python=3.12&gist=54f484ed23e70f7d771f08bf839f8e4e

Expected Behavior

Success: no issues found in 1 source file

Actual Behavior

main.py:20: error: Only @runtime_checkable protocols can be used with instance and class checks  [misc]
Found 1 error in 1 file (checked 1 source file)