Bump protobuf from 3.9.0 to 3.18.3

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.9.0 to 3.18.3.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.9.0...v3.18.3)

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

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

Author: dependabot[bot]

requirements.txt

@@ -45,7 +45,7 @@ msgpack==1.0.0
 numpy==1.18.2
 oauth2client==4.1.2
 Pillow==7.1.1
-protobuf==3.9.1
+protobuf==3.18.3
 pyasn1==0.4.7
 pyasn1-modules==0.2.6
 pycryptodome==3.9.7