[CodeGen] Remove redundant declarations (NFC) (#166105)

In C++17, static constexpr members are implicitly inline, so they no
longer require an out-of-line definition.

Identified with readability-redundant-declaration.

Author: kazutakahirata

llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp

@@ -745,11 +745,6 @@ void AppleAccelTableStaticTypeData::emit(AsmPrinter *Asm) const {
   Asm->emitInt32(QualifiedNameHash);
 }
 
-constexpr AppleAccelTableData::Atom AppleAccelTableTypeData::Atoms[];
-constexpr AppleAccelTableData::Atom AppleAccelTableOffsetData::Atoms[];
-constexpr AppleAccelTableData::Atom AppleAccelTableStaticOffsetData::Atoms[];
-constexpr AppleAccelTableData::Atom AppleAccelTableStaticTypeData::Atoms[];
-
 #ifndef NDEBUG
 void AppleAccelTableWriter::Header::print(raw_ostream &OS) const {
   OS << "Magic: " << format("0x%x", Magic) << "\n"