add blurb suggesting 910/911 if you want to check class methods

Author: jakkdl

docs/rules.rst

@@ -100,6 +100,7 @@ _`ASYNC124`: async-function-could-be-sync
     Calling an async function is slower than calling regular functions, so if possible you
     might want to convert your function to be synchronous.
     This currently overlaps with :ref:`ASYNC910 <ASYNC910>` and :ref:`ASYNC911 <ASYNC911>` which, if enabled, will autofix the function to have :ref:`checkpoint`.
+    This excludes class methods as they often have to be async for other reasons, if you really do want to check those you could manually run :ref:`ASYNC910 <ASYNC910>` and/or :ref:`ASYNC911 <ASYNC911` and check the methods they trigger on.
 
 Blocking sync calls in async functions
 ======================================