Make PIM-invalid log identical to Zino 1

As suggested in code review.

Co-authored-by: Johanna England <[email protected]>

src/zino/trapobservers/logged_traps.py

@@ -86,7 +86,7 @@ async def handle_trap(self, trap: TrapMessage) -> Optional[bool]:
 
         trap_type = "register" if trap.name.endswith("Register") else "join-prune"
         _logger.info(
-            "%s: PIM-invalid-%s: from %s group %s RP %s",
+            "%s PIM-invalid-%s: from %s group %s RP %s",
             trap.agent.device.name,
             trap_type,
             origin,