[MM-52786] webapp/platform/client : Remove dev dependencies in favour of monorepo (#23393)

* init

* Update setupTests.ts

webapp/platform/client/src/setupTests.ts

@@ -0,0 +1,4 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import 'isomorphic-fetch';