cargo: bump futures from 0.3.16 to 0.3.17

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.16 to 0.3.17.
- [Release notes](https://github.com/rust-lang/futures-rs/releases)
- [Changelog](https://github.com/rust-lang/futures-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/futures-rs/compare/0.3.16...0.3.17)

---
updated-dependencies:
- dependency-name: futures
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -32,7 +32,7 @@ dirs = { version = "3.0.2", optional=true }
 email = { git = "https://github.com/deltachat/rust-email", branch = "master" }
 encoded-words = { git = "https://github.com/async-email/encoded-words", branch="master" }
 escaper = "0.1.1"
-futures = "0.3.16"
+futures = "0.3.17"
 hex = "0.4.0"
 image = { version = "0.23.5", default-features=false, features = ["gif", "jpeg", "ico", "png", "pnm", "webp", "bmp"] }
 indexmap = "1.7.0"