Rollup merge of #141873 - neeko-cat:patch-1, r=tgross35

Fixed a typo in `ManuallyDrop`'s doc

I noticed a typo in `ManuallyDrop`'s documentation (someone wrote "iff" instead of "if"). I fixed it in this PR.

Author: matthiaskrgr

library/core/src/mem/manually_drop.rs

@@ -84,7 +84,7 @@ use crate::ptr;
 /// use std::mem::ManuallyDrop;
 ///
 /// pub struct BadOption<T> {
-///     // Invariant: Has been dropped iff `is_some` is false.
+///     // Invariant: Has been dropped if `is_some` is false.
 ///     value: ManuallyDrop<T>,
 ///     is_some: bool,
 /// }