Update cortex-m requirement from 0.6.3 to 0.7.0 (#32)
Update cortex-m requirement from 0.6.3 to 0.7.0 (#32)

Updates the requirements on [cortex-m](https://github.com/rust-embedded/cortex-m) to permit the latest version.
- [Release notes](https://github.com/rust-embedded/cortex-m/releases)
- [Changelog](https://github.com/rust-embedded/cortex-m/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-embedded/cortex-m/compare/v0.6.3...v0.7.0)

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

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
lucasbrendel/xmc4200,lucasbrendel/xmc4200