[NFC][X86][ISel] Remove the unused assert

The condition of assert is always true, so just remove it.
OptForMinSize means hasMinSize(), which is hasFnAttribute(Attribute::MinSize).
hasOptSize() is hasFnAttribute(Attribute::OptimizeForSize) || hasMinSize().
So, '!hasMinSize() || hasFnAttribute(Attribute::OptimizeForSize) || hasMinSize()'
is awalys true.

Author: shining1984

llvm/lib/Target/X86/X86ISelDAGToDAG.cpp

@@ -184,8 +184,6 @@ namespace {
 
       // OptFor[Min]Size are used in pattern predicates that isel is matching.
       OptForMinSize = MF.getFunction().hasMinSize();
-      assert((!OptForMinSize || MF.getFunction().hasOptSize()) &&
-             "OptForMinSize implies OptForSize");
       return SelectionDAGISel::runOnMachineFunction(MF);
     }