[clang] [Sema] LambdaScopeForCallOperatorInstantiationRAII - fix typo in early out logic (PR #96888)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 commented:

Thanks for the patch.
While I think this makes sense, it still confuses me whether there was some redundancy in the guard condition. Do we have any situation where `Pattern` is non-null whereas `ParentFD` becomes null? I assume they are always paired, at least for the lambda cases.

https://github.com/llvm/llvm-project/pull/96888