update metadata with new error

docs/api/runtime-errors.md

 # Runtime errors
 
-There are **194** errors from **37** pallets.
+There are **196** errors from **37** pallets.
 
 <ul>
 <li>System - 0
@@ -909,6 +909,13 @@ Membership already acquired.
 Membership not found.
 </details>
 </li>
+<li>
+<details>
+<summary>
+<code>AlreadyMember</code> - 3</summary>
+Already member, can not claim membership
+</details>
+</li>
 </ul>
 </li>
 <li>Cert - 43
@@ -1191,6 +1198,13 @@ Membership already acquired.
 Membership not found.
 </details>
 </li>
+<li>
+<details>
+<summary>
+<code>AlreadyMember</code> - 3</summary>
+Already member, can not claim membership
+</details>
+</li>
 </ul>
 </li>
 <li>SmithCert - 53