docs(admin): added missing updateUser api (#4846)

docs/content/docs/plugins/admin.mdx

@@ -259,6 +259,29 @@ type setUserPassword = {
 ```
 </APIMethod>
 
+### Update user
+
+Update a user's details.
+
+<APIMethod
+  path="/admin/update-user"
+  method="POST"
+  requireSession
+>
+```ts
+type adminUpdateUser = {
+    /**
+     * The user id which you want to update.
+     */
+    userId: string = "user-id"
+    /**
+     * The data to update.
+     */
+    data: Record<string, any> = { name: "John Doe" }
+}
+```
+</APIMethod>
+
 ### Ban User
 
 Bans a user, preventing them from signing in and revokes all of their existing sessions.