chore: export shorebird_check_for_update for android

Author: felangel

shell/platform/android/android_exports.lst

@@ -17,6 +17,7 @@
     shorebird_free_string;
     shorebird_free_update_result;
     shorebird_check_for_downloadable_update;
+    shorebird_check_for_update;
     shorebird_update;
     shorebird_update_with_result;
     shorebird_next_boot_patch_number;