build(deps-dev): bump pre-commit from 2.17.0 to 2.20.0 in /backend

Bumps [pre-commit](https://github.com/pre-commit/pre-commit) from 2.17.0 to 2.20.0.
- [Release notes](https://github.com/pre-commit/pre-commit/releases)
- [Changelog](https://github.com/pre-commit/pre-commit/blob/main/CHANGELOG.md)
- [Commits](pre-commit/pre-commit@v2.17.0...v2.20.0)

---
updated-dependencies:
- dependency-name: pre-commit
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/requirements-dev.txt

@@ -1,5 +1,5 @@
 fakeredis==1.7.0
-pre-commit==2.17.0
+pre-commit==2.20.0
 pytest==6.2.5
 pytest-responses==0.5.0
 responses==0.17.0