Fix comment about number of roles

This comment is out of date since elastic#71710.

Author: gtback

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/SecurityDocumentationIT.java

@@ -691,7 +691,7 @@ public void testGetRoles() throws Exception {
 
             List<Role> roles = response.getRoles();
             assertNotNull(response);
-            // 29 system roles plus the three we created
+            // 31 system roles plus the three we created
             assertThat(roles.size(), equalTo(31 + 3));
         }