$participants: Don't ping @everyone (#256)

Fixes #253

Author: NMertsch

src/europython_discord/cogs/guild_statistics.py

@@ -37,7 +37,7 @@ async def list_participants(self, ctx: commands.Context) -> None:
         # send message
         lines = [f"{ctx.author.mention} Participant Statistics:"]
         for role_name, count in role_counts.items():
-            lines.append(f"* {count} {role_name}")
+            lines.append(f"* {count} {role_name.strip('<>@')}")
         await ctx.send(content="\n".join(lines))
 
     async def cog_check(self, ctx: commands.Context) -> bool: