Fix comment on the move constructor of `ReturnValueSlot`

`AssumeInitAndTakeValue` leaves the value uninitialized, not moved-from. I rewrote the parenthetical to refer to concepts instead of specific functions.

PiperOrigin-RevId: 546889397
Change-Id: I717f8f3acc59b573d7c736eb4772aeb3bb9454c2
diff --git a/support/internal/return_value_slot.h b/support/internal/return_value_slot.h
index 70b836f..2eb73ff 100644
--- a/support/internal/return_value_slot.h
+++ b/support/internal/return_value_slot.h
@@ -82,9 +82,8 @@
     return return_value;
   }
 
-  // SAFETY REQUIREMENTS: The return value in `other` must have been
-  // initialized.  (It is also okay if the other value is in a moved-away state
-  // after calling `AssumeInitAndTakeValue` on it).
+  // SAFETY REQUIREMENTS: The value contained in `other` must be initialized
+  // (but may be moved-from).
   ReturnValueSlot(ReturnValueSlot&& other) { value_ = std::move(other.value_); }
 
   // Does not destroy the contained value.