chore: update reference in cross-platform test workflow from v8 to main

Author: itaybre

.github/workflows/test-cross-platform.yml

@@ -57,7 +57,7 @@ jobs:
         with:
           repository: getsentry/sentry-react-native
           path: sentry-react-native
-          ref: v8
+          ref: main
 
       - name: Enable Corepack
         working-directory: sentry-react-native