logind: do not emit beep in wall messages

Those may go via the PC speaker, which is annoying and unexpected.
Most people have it off, so this doesn't work reliably anyway, so we can
disable it without much loss.

Fixes #23520.

src/shared/utmp-wtmp.c

@@ -360,7 +360,7 @@ int utmp_wall(
         }
 
         if (asprintf(&text,
-                     "\a\r\n"
+                     "\r\n"
                      "Broadcast message from %s@%s%s%s (%s):\r\n\r\n"
                      "%s\r\n\r\n",
                      un ?: username, hn,