Fix Scrutinizer issues in mod [_well_know -> contactgroup]

- Remove unused variables and parameter
- Updated function documentation
- Fix formatting
- Add back uninitialized variables
- Simplify nested conditions

mod/amcd.php

@@ -2,7 +2,8 @@
 
 use Friendica\App;
 
-function amcd_content(App $a) {
+function amcd_content()
+{
 	echo <<< JSON
 {
   "version":1,
@@ -47,4 +48,4 @@ function amcd_content(App $a) {
 }
 JSON;
 	killme();
-}
+}