Auto merge of #7566 - rust-lang:dependabot/cargo/crossbeam-utils-0.7, r=alexcrichton

Update crossbeam-utils requirement from 0.6 to 0.7

Updates the requirements on [crossbeam-utils](https://github.com/crossbeam-rs/crossbeam) to permit the latest version.
<details>
<summary>Changelog</summary>

*Sourced from [crossbeam-utils's changelog](https://github.com/crossbeam-rs/crossbeam/blob/master/CHANGELOG.md).*

> # Version 0.7.0
>
> - Remove `ArcCell`, `MsQueue`, and `TreiberStack`.
> - Change the interface of `ShardedLock` to match `RwLock`.
> - Add `SegQueue::len()`.
> - Rename `SegQueue::try_pop()` to `SegQueue::pop()`.
> - Change the return type of `SegQueue::pop()` to `Result`.
> - Introduce `ArrayQueue`.
> - Update dependencies.
>
> # Version 0.6.0
>
> - Update dependencies.
>
> # Version 0.5.0
>
> - Update `crossbeam-channel` to 0.3.
> - Update `crossbeam-utils` to 0.6.
> - Add `AtomicCell`, `SharedLock`, and `WaitGroup`.
>
> # Version 0.4.1
>
> - Fix a double-free bug in `MsQueue` and `SegQueue`.
>
> # Version 0.4
>
> - Switch to the new implementation of epoch-based reclamation in
>   [`crossbeam-epoch`](https://github.com/crossbeam-rs/crossbeam-epoch), fixing numerous bugs in the
>   old implementation.  Its API is changed in a backward-incompatible way.
> - Switch to the new implementation of `CachePadded` and scoped thread in
>   [`crossbeam-utils`](https://github.com/crossbeam-rs/crossbeam-utils).  The scoped thread API is
>   changed in a backward-incompatible way.
> - Switch to the new implementation of Chase-Lev deque in
>   [`crossbeam-deque`](https://github.com/crossbeam-rs/crossbeam-deque).  Its API is changed in a
>   backward-incompatible way.
> - Export channel implemented in
>   [`crossbeam-channel`](https://github.com/crossbeam-rs/crossbeam-channel).
> - Remove `AtomicOption`.
> - Implement `Default` and `From` traits.
>
> # Version 0.3
>
> - Introduced `ScopedThreadBuilder` with the ability to name threads and set stack size
> - `Worker` methods in the Chase-Lev deque don't require mutable access anymore
> - Fixed a bug when unblocking `pop()` in `MsQueue`
> - Implemented `Drop` for `MsQueue`, `SegQueue`, and `TreiberStack`
> - Implemented `Default` for `TreiberStack`
> - Added `is_empty` to `SegQueue`
> - Renamed `mem::epoch` to `epoch`
> - Other bug fixes
></tr></table> ... (truncated)
</details>
<details>
<summary>Commits</summary>

- [`28ad2b7`](https://github.com/crossbeam-rs/crossbeam/commit/28ad2b7e015832b47db7e389dd9ebce3e94b3adb) Update versions in readmes
- [`c98fea1`](https://github.com/crossbeam-rs/crossbeam/commit/c98fea12e67447d71065539fe2cdde545ea57d8b) Merge [#444](https://github-redirect.dependabot.com/crossbeam-rs/crossbeam/issues/444)
- [`d953f49`](https://github.com/crossbeam-rs/crossbeam/commit/d953f49ecc7eb5fe6c271b018a4a753ba435ee58) Add compatibility section to readme
- [`c76f145`](https://github.com/crossbeam-rs/crossbeam/commit/c76f1451820009bb81bbc0ccf782eb976637667f) Prepare for the next release
- [`99762ee`](https://github.com/crossbeam-rs/crossbeam/commit/99762ee63333fcd7b9abcd1c5ede835cba68c438) Merge [#442](https://github-redirect.dependabot.com/crossbeam-rs/crossbeam/issues/442)
- [`ebb6b5f`](https://github.com/crossbeam-rs/crossbeam/commit/ebb6b5fe6d7423a97a7762fa5fde7cb2d801fd39) Do not perform superfluous bounds checks on drop
- [`d2ab7a5`](https://github.com/crossbeam-rs/crossbeam/commit/d2ab7a5c437322e01de7807e3a7803249ec28d20) Update LICENSE-APACHE
- [`f54db88`](https://github.com/crossbeam-rs/crossbeam/commit/f54db88d1a66eea8338176ae288b91a26764f7b7) Merge [#437](https://github-redirect.dependabot.com/crossbeam-rs/crossbeam/issues/437)
- [`caa52c4`](https://github.com/crossbeam-rs/crossbeam/commit/caa52c4e841c11bf2a26489635696080d7deca21) Merge [#436](https://github-redirect.dependabot.com/crossbeam-rs/crossbeam/issues/436)
- [`af68803`](https://github.com/crossbeam-rs/crossbeam/commit/af688031a219f6586b7e8e54719087bc0a1bc693) Merge [#438](https://github-redirect.dependabot.com/crossbeam-rs/crossbeam/issues/438)
- Additional commits viewable in [compare view](https://github.com/crossbeam-rs/crossbeam/compare/crossbeam-utils-0.6.0...crossbeam-utils-0.7.0)
</details>
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