docs: clarify that log filters remove lines if the filter matches

Signed-off-by: Xe Iaso <me@xeiaso.net>

data/botPolicies.yaml

@@ -142,11 +142,16 @@ logging:
   filters:
     # Every filter must have a name and an expression. You can use the same expression
     # syntax as you can with bots or thresholds.
+    #
+    # If the expression returns `true`, then the log line is filtered _out_.
     - name: "http-stdlib"
+      # Log lines where the message starts with "http:" are filtered out.
       expression: msg.startsWith("http:")
     - name: "context-canceled"
+      # Log lines relating to context cancellation are filtered out.
       expression: msg.contains("context canceled")
     - name: "http-pipelining"
+      # Log lines relating to HTTP/1.1 pipelining being improperly handled are filtered out.
       expression: msg.contains("Unsolicited response received on idle HTTP channel")
 
 # Open Graph passthrough configuration, see here for more information: