[clang] Remove redundant member initialization (NFC)

clang/include/clang/AST/ASTConcept.h

clang/include/clang/ASTMatchers/Dynamic/Diagnostics.h

clang/include/clang/Basic/Diagnostic.h

clang/include/clang/Basic/PartialDiagnostic.h

clang/include/clang/Parse/Parser.h

clang/include/clang/Sema/ParsedAttr.h

clang/include/clang/Sema/ParsedTemplate.h

clang/lib/AST/MicrosoftCXXABI.cpp

clang/lib/Sema/Sema.cpp

clang/lib/Sema/SemaExprCXX.cpp

clang/utils/TableGen/MveEmitter.cpp