Disallow users to set theme as a project-level setting (#3312)

* Disallow users to set theme as a project-level setting

* A snapshot a day keeps the bugs away! 📷🐛 (OS: ubuntu)

* Fix up tests that assumed theme could be set at project level

* Missed two more tests that assumed theme was a project-level setting

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Co-authored-by: Jess Frazelle <jessfraz@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

src/lib/settings/initialSettings.tsx

@@ -114,6 +114,7 @@ export function createSettings() {
        * The overall appearance of the app: light, dark, or system
        */
       theme: new Setting<Themes>({
+        hideOnLevel: 'project',
         defaultValue: Themes.System,
         description: 'The overall appearance of the app',
         validate: (v) => isEnumMember(v, Themes),