Auto-joining threads can run into a 400
Sentry Issue: [BOT-1RE](https://sentry.io/organizations/python-discord/issues/2848940096/?referrer=github_integration)

We should be adding `HTTPException` to the `contextlib.suppress` just above the `thread.join()` call.
```
HTTPException: 400 Bad Request (error code: 50083): Thread is archived
  File "discord/http.py", line 335, in request
    raise HTTPException(response, data)
  File "discord/threads.py", line 607, in join
    await self._state.http.join_thread(self.id)
  File "bot/exts/utils/bot.py", line 32, in on_thread_join
    await thread.join()
  File "discord/client.py", line 351, in _run_event
    await coro(*args, **kwargs)

Unhandled exception in on_thread_join.
```
diff --git a/bot/exts/utils/bot.py b/bot/exts/utils/bot.py
index 78869277..8f0094bc 100644
--- a/bot/exts/utils/bot.py
+++ b/bot/exts/utils/bot.py
@@ -1,7 +1,6 @@
-from contextlib import suppress
 from typing import Optional
 
-from discord import Embed, Forbidden, TextChannel, Thread
+from discord import Embed, TextChannel
 from discord.ext.commands import Cog, Context, command, group, has_any_role
 
 from bot.bot import Bot
@@ -17,20 +16,6 @@ class BotCog(Cog, name="Bot"):
     def __init__(self, bot: Bot):
         self.bot = bot
 
-    @Cog.listener()
-    async def on_thread_join(self, thread: Thread) -> None:
-        """
-        Try to join newly created threads.
-
-        Despite the event name being misleading, this is dispatched when new threads are created.
-        """
-        if thread.me:
-            # We have already joined this thread
-            return
-
-        with suppress(Forbidden):
-            await thread.join()
-
     @group(invoke_without_command=True, name="bot", hidden=True)
     async def botinfo_group(self, ctx: Context) -> None:
         """Bot informational commands."""
['bot/exts/utils/bot.py']