Rollup merge of rust-lang#83740 - obi1kenobi:patch-1, r=joshtriplett

Fix comment typo in once.rs

I believe I came across a minor typo in a comment. I am not particularly familiar with this part of the codebase, but I have read the surrounding code as well as the referenced `park` and `unpark` functions, and I believe my proposed change is true to the intended meaning of the comment.

I intentionally tried to keep the change as minimal as possible. If I have the maintainers' permission, I'd also love to add a comma to improve readability as follows: `Luckily ``park`` comes with the guarantee that if it got an ``unpark`` just before on an unparked thread, it does not park.`

library/std/src/sync/once.rs

@@ -471,7 +471,7 @@ fn wait(state_and_queue: &AtomicUsize, mut current_state: usize) {
             // If the managing thread happens to signal and unpark us before we
             // can park ourselves, the result could be this thread never gets
             // unparked. Luckily `park` comes with the guarantee that if it got
-            // an `unpark` just before on an unparked thread is does not park.
+            // an `unpark` just before on an unparked thread it does not park.
             thread::park();
         }
         break;