Fix a DeprecationWarning about the Flask.static_path parameter. (getr…

…edash#3624)

Code: https://github.com/pallets/flask/blob/d1d82ca8ce7262ad9d27245ce44f86571287810e/flask/app.py#L347-L351

redash/__init__.py

@@ -110,7 +110,7 @@ def create_app():
     app = Flask(__name__,
                 template_folder=settings.STATIC_ASSETS_PATH,
                 static_folder=settings.STATIC_ASSETS_PATH,
-                static_path='/static')
+                static_url_path='/static')
 
     # Make sure we get the right referral address even behind proxies like nginx.
     app.wsgi_app = ProxyFix(app.wsgi_app, settings.PROXIES_COUNT)