Remove unused 'using' declaration. Found by clang-tidy: misc-unused-using-decls NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293382 91177308-0d34-0410-b5e6-96231b3b80d8

Author: sylvestre

tools/llvm-xray/xray-converter.cc

@@ -84,7 +84,6 @@ static cl::alias InstrMapFormat2("t", cl::aliasopt(InstrMapFormat),
                                  cl::desc("Alias for -instr-map-format"),
                                  cl::sub(Convert));
 
-using llvm::yaml::IO;
 using llvm::yaml::Output;
 
 void TraceConverter::exportAsYAML(const Trace &Records, raw_ostream &OS) {