Update comment

Author: lukel97

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -13552,7 +13552,7 @@ enum ExtKind : uint8_t { ZExt = 1 << 0, SExt = 1 << 1, FPExt = 1 << 2 };
 /// NodeExtensionHelper for `a` and one for `b`.
 ///
 /// This class abstracts away how the extension is materialized and
-/// how its Mask, VL, number of users affect the combines.
+/// how its number of users affect the combines.
 ///
 /// In particular:
 /// - VWADD_W is conceptually == add(op0, sext(op1))