changed double-quote to single-quote for consistency

config.py

@@ -4,6 +4,6 @@ class Config:
     gitlab_api_key = None
 
     # Canvas API configuration
-    canvas_url = "https://canvas.unl.edu/api/v1/"
+    canvas_url = 'https://canvas.unl.edu/api/v1/'
     canvas_api_key = None