fix(crashlytics, android): suppress unchecked cast warning (#16864)

Author: SelaseKay

packages/firebase_crashlytics/firebase_crashlytics/android/src/main/java/io/flutter/plugins/firebase/crashlytics/FlutterFirebaseCrashlyticsPlugin.java

@@ -148,6 +148,7 @@ private Task<Void> recordError(final Map<String, Object> arguments) {
             final boolean fatal = (boolean) Objects.requireNonNull(arguments.get(Constants.FATAL));
             final String buildId =
                 (String) Objects.requireNonNull(arguments.get(Constants.BUILD_ID));
+            @SuppressWarnings("unchecked")
             final List<String> loadingUnits =
                 (List<String>) Objects.requireNonNull(arguments.get(Constants.LOADING_UNITS));