[NFC][clang] cleanup dead code (llvm#164977)

Dead code probably left-over of some PR refactoring.

Author: Keenuts

clang/lib/Parse/ParseHLSL.cpp

@@ -126,15 +126,9 @@ Parser::ParsedSemantic Parser::ParseHLSLSemantic() {
  // semantic index. The semantic index is the number at the end of
  // the semantic, including leading zeroes. Digits located before
  // the last letter are part of the semantic name.
- bool Invalid = false;
  SmallString<256> Buffer;
  Buffer.resize(Tok.getLength() + 1);
  StringRef Identifier = PP.getSpelling(Tok, Buffer);
- if (Invalid) {
- Diag(Tok.getLocation(), diag::err_expected_semantic_identifier);
- return {};
- }
-
  assert(Identifier.size() > 0);
  // Determine the start of the semantic index.
  unsigned IndexIndex = Identifier.find_last_not_of("0123456789") + 1;