Bump polyline from 2.0.3 to 2.0.4 in /backend

Bumps [polyline](https://github.com/frederickjansen/polyline) from 2.0.3 to 2.0.4.
- [Release notes](https://github.com/frederickjansen/polyline/releases)
- [Commits](frederickjansen/polyline@v2.0.3...v2.0.4)

---
updated-dependencies:
- dependency-name: polyline
  dependency-version: 2.0.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -7,5 +7,5 @@ geopy==2.4.1
 openpyxl==3.1.5
 grequests==0.7.0
 pyclustering==0.10.1.2
-polyline==2.0.3
+polyline==2.0.4
 pypdf==6.4.0