Fixed Attributes.h comment typo from vecctor to vector

--

PiperOrigin-RevId: 248369005
diff --git a/include/mlir/IR/Attributes.h b/include/mlir/IR/Attributes.h
index a476af7..8305bbb 100644
--- a/include/mlir/IR/Attributes.h
+++ b/include/mlir/IR/Attributes.h
@@ -430,7 +430,7 @@
   }
 };
 
-/// An attribute that represents a reference to a splat vecctor or tensor
+/// An attribute that represents a reference to a splat vector or tensor
 /// constant, meaning all of the elements have the same value.
 class SplatElementsAttr
     : public Attribute::AttrBase<SplatElementsAttr, ElementsAttr,