build(deps): bump protobuf from 3.19.1 to 3.19.5 in /backend

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.19.1 to 3.19.5.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.19.1...v3.19.5)

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

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

Author: dependabot[bot]

backend/requirements.txt

@@ -94,7 +94,7 @@ pluggy==1.0.0
 pre-commit==2.15.0
 premailer==3.10.0
 prompt-toolkit==3.0.24
-protobuf==3.19.1
+protobuf==3.19.5
 ptyprocess==0.7.0
 py==1.11.0
 pyclipper==1.3.0.post4