Make the index increment unchecked in UnsafeRawBufferPointer.Iterator.next

Author: meg-gupta

stdlib/public/core/UnsafeRawBufferPointer.swift.gyb

@@ -170,7 +170,7 @@ extension UnsafeRawBufferPointer.Iterator: IteratorProtocol, Sequence {
     // Validly constructed buffer pointers also have an _end that is strictly
     // greater than or equal to _position.
     // So we do not need to do checked arithmetic here as we cannot possibly overflow.
-    _position = position + 1
+    _position = position &+ 1
     return result
   }
 }