Update metadata for ca.uwaterloo.Raven

[razzeee]

This PR updates the metadata to improve discoverability and user experience for Raven.

---

🏷️ Keywords

- hydrology
- watershed modeling
- flow simulation

---

Generated by Metadata Bot 🤖

[flathubbot]

🚧 Test build enqueued.

[flathubbot]

🚧 Started test build.

[flathubbot]

✅ Test build succeeded. To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/230472/ca.uwaterloo.Raven.flatpakref

Built for aarch64 and x86_64 architectures.

⚠️ Linter warnings:

Warnings can be promoted to errors in the future. Please try to resolve them.

• 'runtime-is-eol-org.freedesktop.Platform-23.08' warning found in linter manifest check.
• 'runtime-is-eol-org.freedesktop.Platform-23.08' warning found in linter repo check.