[Web] Add missing string

data/web/lang/lang.en.php

@@ -435,6 +435,7 @@ $lang['diagnostics']['optional'] = 'This record is optional.';
 $lang['diagnostics']['cname_from_a'] = 'Value derived from A/AAAA record. This is supported as long as the record points to the correct resource.';
 
 $lang['admin']['relay_from'] = '"From:" address';
+$lang['admin']['relay_run'] = "Run test";
 $lang['admin']['api_allow_from'] = "Allow API access from these IPs";
 $lang['admin']['api_key'] = "API key";
 $lang['admin']['activate_api'] = "Activate API";