chore: drop editor-only Rider and test framework packages

Neither ships into the player, so the APK is unaffected. Removing
them just keeps the manifest focused on what the demo actually uses
and trims a few hundred MB out of Library/PackageCache on cold CI
runners.

- com.unity.ide.rider: Rider IDE integration, editor-only. Anyone
  using Rider locally can add it back to their own copy or rely on
  Rider's own Unity Editor plugin.
- com.unity.test-framework: no [Test] / [UnityTest] / TestRunner /
  nunit references anywhere in the repo; demo has zero PlayMode or
  EditMode tests and no asmdef references the package.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: fadi-george

examples/demo/Packages/manifest.json

@@ -3,10 +3,8 @@
     "com.onesignal.unity.android": "file:../../../com.onesignal.unity.android",
     "com.onesignal.unity.core": "file:../../../com.onesignal.unity.core",
     "com.onesignal.unity.ios": "file:../../../com.onesignal.unity.ios",
-    "com.unity.ide.rider": "3.0.39",
     "com.unity.inputsystem": "1.19.0",
     "com.unity.nuget.newtonsoft-json": "3.2.2",
-    "com.unity.test-framework": "1.6.0",
     "com.unity.modules.accessibility": "1.0.0",
     "com.unity.modules.androidjni": "1.0.0",
     "com.unity.modules.jsonserialize": "1.0.0",