alloc: remove repeated word in comment

Linux's `checkpatch.pl` reports:

```txt
#42544: FILE: rust/alloc/vec/mod.rs:2692:
WARNING: Possible repeated word: 'to'
+            // - Elements are :Copy so it's OK to to copy them, without doing
```

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index d222fcb445f..fa3fbb86582 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -2470,7 +2470,7 @@ impl<T: Copy, A: Allocator> ExtendFromWithinSpec for Vec<T, A> {
             // SAFETY:
             // - Both pointers are created from unique slice references (`&mut [_]`)
             //   so they are valid and do not overlap.
-            // - Elements are :Copy so it's OK to to copy them, without doing
+            // - Elements are :Copy so it's OK to copy them, without doing
             //   anything with the original values
             // - `count` is equal to the len of `source`, so source is valid for
             //   `count` reads