(docs) proxy - fail requests with custom error message

docs/my-website/docs/proxy/rules.md

@@ -8,9 +8,12 @@ Use this to fail a request based on the output of an llm api call.
 
 ```python
 def my_custom_rule(input): # receives the model response 
-    if len(input) < 5: # trigger fallback if the model response is too short
-         return False 
-    return True 
+    if len(input) < 5: 
+      return {
+            "decision": False,
+            "message": "This violates LiteLLM Proxy Rules. Response too short"
+      }
+    return {"decision": True}   # message not required since, request will pass
 ```
 
 ### Step 2. Point it to your proxy
@@ -18,7 +21,6 @@ def my_custom_rule(input): # receives the model response
 ```python
 litellm_settings:
   post_call_rules: post_call_rules.my_custom_rule
-  num_retries: 3
 ```
 
 ### Step 3. Start + test your proxy
@@ -32,7 +34,7 @@ curl --location 'http://0.0.0.0:8000/v1/chat/completions' \
 --header 'Content-Type: application/json' \
 --header 'Authorization: Bearer sk-1234' \
 --data '{
-  "model": "deepseek-coder",
+  "model": "gpt-3.5-turbo",
   "messages": [{"role":"user","content":"What llm are you?"}],
   "temperature": 0.7,
   "max_tokens": 10,