docs: Fix the wrong links in secret documentation

docs/formatsecret.html.in: (s/domain\.html/formatdomain\.html/g)

docs/formatsecret.html.in

@@ -64,7 +64,7 @@
       a single <code>name</code> element that specifies a usage name
       for the secret.  The Ceph secret can then be used by UUID or by
       this usage name via the <code>&lt;auth&gt;</code> element of
-      a <a href="domain.html#elementsDisks">disk
+      a <a href="formatdomain.html#elementsDisks">disk
       device</a>. <span class="since">Since 0.9.7</span>.
     </p>
 
@@ -76,7 +76,7 @@
       a single <code>target</code> element that specifies a usage name
       for the secret.  The iSCSI secret can then be used by UUID or by
       this usage name via the <code>&lt;auth&gt;</code> element of
-      a <a href="domain.html#elementsDisks">disk
+      a <a href="formatdomain.html#elementsDisks">disk
       device</a>. <span class="since">Since 1.0.4</span>.
     </p>