[clang] Fix a typo-correction crash

We leave a dangling TypoExpr when typo-correction is performed
successfully in `checkArgsForPlaceholders`, which leads a crash in the
later TypoCorrection.

This code was added in https://github.com/llvm/llvm-project/commit/1586782767938df3a20f7abc4d8335c48b100bc4,
and it didn't seem to have enough test coverage.
The fix is to remove this part, and no failuer tests.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D87815