Update flask requirement from <2.4,>=2.3 to >=2.3,<3.1

Updates the requirements on [flask](https://github.com/pallets/flask) to permit the latest version.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@2.3.0...3.0.0)

---
updated-dependencies:
- dependency-name: flask
  dependency-type: direct:production
...

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

pyproject.toml

@@ -36,7 +36,7 @@ dependencies = [
 
 [project.optional-dependencies]
 online = [
-    "flask>=2.3,<2.4",
+    "flask>=2.3,<3.1",
     "flask-cors>=3.0,<4.1",
     "panoptes-client>=1.6,<1.7",
     "requests>=2.28,<2.32",