fix(CI): Fix video verification tests

Searching for "master" doesn't work when the app switches to "main"

Signed-off-by: Joas Schilling <[email protected]>

.drone.yml

@@ -1241,7 +1241,7 @@ steps:
   commands:
     # JavaScript files are not used in integration tests, so it is not needed to
     # build them.
-    - git clone --depth 1 --branch main https://github.com/nextcloud/spreed apps/spreed
+    - git clone --depth 1 --branch stable28 https://github.com/nextcloud/spreed apps/spreed
     - cd apps/spreed
     - composer --version
     - composer self-update --2