Bump stm32f4xx-hal in /examples/stm32f4-single-motor-example

Bumps [stm32f4xx-hal](https://github.com/stm32-rs/stm32f4xx-hal) from 0.22.0 to 0.22.1.
- [Release notes](https://github.com/stm32-rs/stm32f4xx-hal/releases)
- [Changelog](https://github.com/stm32-rs/stm32f4xx-hal/blob/master/CHANGELOG.md)
- [Commits](stm32-rs/stm32f4xx-hal@v0.22.0...v0.22.1)

---
updated-dependencies:
- dependency-name: stm32f4xx-hal
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]