Bump fastapi from 0.115.6 to 0.115.8

Bumps [fastapi](https://github.com/fastapi/fastapi) from 0.115.6 to 0.115.8.
- [Release notes](https://github.com/fastapi/fastapi/releases)
- [Commits](fastapi/fastapi@0.115.6...0.115.8)

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

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

requirements.demo.txt

@@ -5,7 +5,7 @@ shapely==2.0.6
 osmnx==2.0.1
 # geopandas==1.0.1 # osmnx 1.9.4 depends on geopandas<0.15 and >=0.12
 uvicorn[standard]==0.34.0
-fastapi==0.115.6
+fastapi==0.115.8
 # following required for isochrones
 scipy==1.15.0
 odbcutils==0.2.1