remove single char conversion function

Author: abhina-sree

llvm/include/llvm/Support/CharSet.h

@@ -138,12 +138,6 @@ class CharSetConverter {
     return EC;
   }
 
-  char convert(char SingleChar) const {
-    SmallString<1> Result;
-    Converter->convert(StringRef(&SingleChar, 1), Result, false);
-    return Result[0];
-  }
-
   std::error_code flush() const { return Converter->flush(); }
 
   std::error_code flush(SmallVectorImpl<char> &Result) const {