Fix group command mention

bot.py

@@ -434,7 +434,7 @@ async def group_command(ctx: commands.Context, subcommand: Optional[str], arg: O
             for member in members:
                 await member.add_roles(role, reason="Create group " + arg)
         await asyncio.sleep(5)
-        await channel.send("Hi, @" + role.name)
+        await channel.send("Hi, " + role.mention)
         await ctx.send("Done :)")