Revert "[YAML] Init local var not set by some branches" (#123238)

Reverts #123137

It's a bug according to
#123137 (review)

Author: vitalybuka

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -1588,7 +1588,7 @@ static bool isInteger(StringRef Val) {
 
 void MappingTraits<std::unique_ptr<ELFYAML::Chunk>>::mapping(
     IO &IO, std::unique_ptr<ELFYAML::Chunk> &Section) {
-  ELFYAML::ELF_SHT Type = ELF::ET_NONE;
+  ELFYAML::ELF_SHT Type;
   StringRef TypeStr;
   if (IO.outputting()) {
     if (auto *S = dyn_cast<ELFYAML::Section>(Section.get()))