Remove unnecessary MCExpr.h include from MCSymbol.h

MCSymbol.h already forwards declares MCExpr and only uses MCExpr* so doesn't
need to include the header.

llvm-svn: 239626

llvm/include/llvm/MC/MCSymbol.h

@@ -17,7 +17,6 @@
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/MC/MCAssembler.h"
-#include "llvm/MC/MCExpr.h"
 #include "llvm/Support/Compiler.h"
 
 namespace llvm {