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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239626 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed