Bump fastapi from 0.115.6 to 0.115.8 in /.github/dependabot

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]>

.github/dependabot/constraints.txt

@@ -1,5 +1,5 @@
 aiohttp==3.11.11
-fastapi==0.115.6
+fastapi==0.115.8
 python-dateutil==2.9.0.post0
 python-dotenv==1.0.1
 requests==2.32.3