Fixing syntax error

VideoColorizerColab.ipynb

@@ -285,7 +285,7 @@
    },
    "outputs": [],
    "source": [
-    "colorizer = get_video_colorizer(render_factor=render_factor, artistic=!stable)"
+    "colorizer = get_video_colorizer(render_factor=render_factor, artistic!=stable)"
    ]
   },
   {