Update Rust crate futures-util to v0.3.21

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
futures-util	dependencies	patch	=0.3.19 -> =0.3.21

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Configuration

📅 Schedule: At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• If you want to rebase/retry this PR, click this checkbox.

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This PR has been generated by WhiteSource Renovate. View repository job log here.

[Turbo87]

@bors r+

[bors]

📌 Commit 6369322 has been approved by Turbo87

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout renovate/futures-util-0.x (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self renovate/futures-util-0.x --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging Cargo.toml
CONFLICT (content): Merge conflict in Cargo.toml
Auto-merging Cargo.lock
Automatic merge failed; fix conflicts and then commit the result.

[bors]

☔ The latest upstream changes (presumably #4533) made this pull request unmergeable. Please resolve the merge conflicts.

[Turbo87]

@bors r+

[bors]

📌 Commit caf44c8 has been approved by Turbo87

[bors]

⌛ Testing commit caf44c8 with merge d907f42...

[bors]

☀️ Test successful - checks-actions
Approved by: Turbo87
Pushing d907f42 to master...