Update NimBLE-Arduino requirement from ^1.4.3 to ^2.1.0 (#120)

Updates the requirements on [NimBLE-Arduino](https://github.com/h2zero/NimBLE-Arduino) to permit the latest version.
- [Release notes](https://github.com/h2zero/NimBLE-Arduino/releases)
- [Commits](https://github.com/h2zero/NimBLE-Arduino/commits/267d8a69665ae29532c191438415092cfd1bf9d7)

---
updated-dependencies:
- dependency-name: NimBLE-Arduino
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Matthias Prinke <[email protected]>