[UPDATE] Update environs requirement

Updates the requirements on [environs](https://github.com/sloria/environs) to permit the latest version.
- [Changelog](https://github.com/sloria/environs/blob/main/CHANGELOG.md)
- [Commits](https://github.com/sloria/environs/compare/14.5.0...15.0.0)

---
updated-dependencies:
- dependency-name: environs
  dependency-version: 15.0.0
  dependency-type: direct:production
...

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

pyproject.toml

@@ -45,7 +45,7 @@ dependencies = [
     "pydantic-extra-types>=2.11.0,<3.0.0",
     "ical>=11.1.0,<12",
     "redis[hiredis]>=5.3.0,<8.0.0",
-    "environs[django]>=14.5.0,<15.0.0",
+    "environs[django]>=14.5.0,<16.0.0",
     "requests>=2.32.5,<3.0.0",
     "honcho>=2.0.0",
     "psutil>=7.2.2,<8.0.0",