metrics: Add ticket 40546 changes file and code fix

The MR was using an old function definition so the code fix is for that.

Closes #40546

Signed-off-by: David Goulet <dgoulet@torproject.org>

changes/ticket40546

@@ -0,0 +1,3 @@
+  o Minor feature (MetricsPort, relay):
+    - Expose time until online keys expires on the MetricsPort. Closes ticket
+      40546.

src/feature/relay/relay_metrics.c

@@ -1014,7 +1014,7 @@ fill_signing_cert_expiry(void)
     signing_key = get_master_signing_key_cert();
     if (signing_key) {
       sentry = metrics_store_add(the_store, rentry->type, rentry->name,
-                                 rentry->help);
+                                 rentry->help, 0, NULL);
       metrics_store_entry_update(sentry, signing_key->valid_until);
     }
   }