Revert "reapply [llvm] add support for mustache templating language (llvm#130876)"

This reverts commit 6bf0c46.

Author: PeterChou1

llvm/include/llvm/Support/Mustache.h

@@ -220,7 +220,6 @@ add_llvm_component_library(LLVMSupport
   MD5.cpp
   MSP430Attributes.cpp
   MSP430AttributeParser.cpp
-  Mustache.cpp      
   NativeFormatting.cpp
   OptimizedStructLayout.cpp
   Optional.cpp