[Sema] Fix c23 not checking CheckBoolLikeConversion (#79588)

Fixes issue #79435 

Checks for implicit conversion into boolean was previously triggered by
`CheckBoolLikeConversion` for C.
When `bool` as a keyword was introduced in C23,
`CheckBoolLikeConversion` would no longer trigger when using `-std=c23`,
but since logical operators and conditional statements still operate on
scalar values, the checks for implicit conversion into bool were never
triggered.

This fix changes `CheckBoolLikeConversion` to not return early for C23,
even though it has support for bools.