Add information about building docs (#10998)

tasks.py

@@ -1904,7 +1904,7 @@ def doc_schema(c):
 @task(
     help={
         'address': 'Host and port to run the server on (default: localhost:8080)',
-        'compile_schema': 'Compile the schema documentation first (default: False)',
+        'compile_schema': 'Compile the API schema documentation first (default: False)',
     }
 )
 def docs_server(c, address='localhost:8080', compile_schema=False):