Add a sleep of 2 seconds so copy-pasting the snippet won't cause a FloodWaitError

Retrieving-all-dialogs.md

@@ -3,7 +3,7 @@ There are several `offset_xyz=` parameters that have no effect at all, but there
 ```python
 from telethon.tl.functions.messages import GetDialogsRequest
 from telethon.tl.types import InputPeerEmpty
-
+from time import sleep
 
 dialogs = []
 users = []
@@ -24,4 +24,5 @@ while True:
     last_date = min(msg.date for msg in result.messages)
     if not result.dialogs:
         break
+    sleep(2)
 ```