libsystemd: sd_journal_get_seqnum() must be tagged with 254 symver, not 253

This is a follow-up for b1712fabd1 which
was prepped for 253, but merged into early 254 development cycle. It
thus had the symbol it adds at the wrong symver. Fix thta.

src/libsystemd/libsystemd.sym

@@ -810,11 +810,11 @@ global:
         sd_pidfd_get_unit;
         sd_pidfd_get_user_slice;
         sd_pidfd_get_user_unit;
-        sd_journal_get_seqnum;
 } LIBSYSTEMD_252;
 
 LIBSYSTEMD_254 {
 global:
+        sd_journal_get_seqnum;
         sd_session_get_username;
         sd_session_get_start_time;
 } LIBSYSTEMD_253;