Bump protobuf from 3.10.0 to 3.15.0

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.10.0 to 3.15.0.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.10.0...v3.15.0)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-type: direct:production
...

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

requirements.txt

@@ -35,7 +35,7 @@ pathtools==0.1.2
 Pillow==8.2.0
 playsound==1.2.2
 proglog==0.1.9
-protobuf==3.10.0
+protobuf==3.15.0
 PyAudio Wheel/PyAudio-0.2.11-cp37-cp37m-win_amd64.whl
 pycparser==2.20
 pymongo==3.11.4