Auto merge of #4533 - rust-lang:renovate/futures-channel-0.x, r=Turbo87

Update Rust crate futures-channel to v0.3.21

[![WhiteSource Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [futures-channel](https://crates.io/crates/futures-channel) | dependencies | patch | `=0.3.19` -> `=0.3.21` |

---

### 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.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click this checkbox.

---

This PR has been generated by [WhiteSource Renovate](https://renovate.whitesourcesoftware.com). View repository job log [here](https://app.renovatebot.com/dashboard#github/rust-lang/crates.io).

Author: bors

Cargo.lock

@@ -55,7 +55,7 @@ diesel_full_text_search = "=1.0.1"
 diesel_migrations = { version = "=1.4.0", features = ["postgres"] }
 dotenv = "=0.15.0"
 flate2 = "=1.0.22"
-futures-channel = { version = "=0.3.19", default-features = false }
+futures-channel = { version = "=0.3.21", default-features = false }
 futures-util = "=0.3.19"
 hex = "=0.4.3"
 http = "=0.2.6"