Revert "[NFC] Fix getSourceLanguage build after llvm commit 6cba572 (KhronosGroup#3385)"

This reverts commit daba8b2.

Author: simeonschaub

lib/SPIRV/LLVMToSPIRVDbgTran.cpp

@@ -587,8 +587,8 @@ SPIRVEntry *LLVMToSPIRVDbgTran::transDbgCompileUnit(const DICompileUnit *CU) {
   if (isNonSemanticDebugInfo())
     generateBuildIdentifierAndStoragePath(CU);
 
-  auto DwarfLang = static_cast<llvm::dwarf::SourceLanguage>(
-      CU->getSourceLanguage().getUnversionedName());
+  auto DwarfLang =
+      static_cast<llvm::dwarf::SourceLanguage>(CU->getSourceLanguage());
   Ops[LanguageIdx] =
       BM->getDebugInfoEIS() == SPIRVEIS_NonSemantic_Shader_DebugInfo_200
           ? convertDWARFSourceLangToSPIRVNonSemanticDbgInfo(DwarfLang)