CLEANUP: dns: remove duplicate code in src/dns.c

issue was identified by cppcheck

[src/dns.c:2037] -> [src/dns.c:2041]: (warning) Variable 'appctx->st2' is reassigned a value before the old one has been used. 'break;' missing?
diff --git a/src/dns.c b/src/dns.c
index c5bed59..5fe44d4 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -2027,8 +2027,6 @@
 			si->flags |= SI_FL_WAIT_ROOM;
 			return 0;
 		}
-
-		appctx->st2 = STAT_ST_FIN;
 		/* fall through */
 
 	default: