Bump protobuf from 3.11.3 to 3.15.0 in /hyperlpr_py3

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.11.3 to 3.15.0.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.11.3...v3.15.0)

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

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

hyperlpr_py3/requirements.txt

@@ -32,7 +32,7 @@ numpy==1.17.4
 opencv-contrib-python==3.4.2.16
 opencv-python==3.4.2.16
 Pillow==7.0.0
-protobuf==3.11.3
+protobuf==3.15.0
 pyparsing==2.4.6
 python-dateutil==2.8.1
 python-editor==1.0.4