[docs] rewrite commands, update samples

docs/guides/samples/groups.cs

@@ -1,15 +1,18 @@
 [Group("admin")]
 public class AdminModule : ModuleBase
 {
-    [Group("mod")]
-    public class ModerationGroup : ModuleBase
+    [Group("clean")]
+    public class CleanModule : ModuleBase
     {
-        // ~admin mod ban foxbot#0282
-        [Command("ban")]
-        public async Task Ban(IGuildUser user) { }
-    }
+        // ~admin clean 15
+        [Command]
+        public async Task Default(int count = 10) => Messages(count);
 
-    // ~admin clean 100
-    [Command("clean")]
-    public async Task Clean(int count = 100) { }
+        // ~admin clean messages 15
+        [Command("messages")]
+        public async Task Messages(int count = 10) { }
+    }
+    // ~admin ban foxbot#0282
+    [Command("ban")]
+    public async Task Ban(IGuildUser user) { }
 }