Remove reroll reaction at max embed length

Once the number of characters in the embed's title exceeds the limit of 256, the bot will remove the reroll emoji.

Suggested (here)[python-discord#1148 (comment)]

bot/exts/utilities/conversationstarters.py

@@ -43,12 +43,14 @@ def __init__(self, bot: Bot):
         self.bot = bot
 
     @staticmethod
-    def _build_topic_embed(channel_id: int, previous_topic: None | str) -> discord.Embed:
+    def _build_topic_embed(channel_id: int, previous_topic: None | str) -> tuple[discord.Embed, bool]:
         """
         Build an embed containing a conversation topic.
 
         If in a Python channel, a python-related topic will be given.
         Otherwise, a random conversation topic will be received by the user.
+
+        Also returns a value that determines whether or not to remove the reaction afterwards
         """
         # No matter what, the form will be shown.
         embed = discord.Embed(
@@ -66,7 +68,7 @@ def _build_topic_embed(channel_id: int, previous_topic: None | str) -> discord.E
 
         if previous_topic is None:
             # This is the first topic being sent
-            return embed
+            return embed, False
 
         total_topics = previous_topic.count("\n") + 1
         # Add 1 before first topic
@@ -78,8 +80,9 @@ def _build_topic_embed(channel_id: int, previous_topic: None | str) -> discord.E
         # When the embed will be larger than the limit, use the previous embed instead
         if len(embed.title) > 256:
             embed.title = previous_topic
+            return embed, True
 
-        return embed
+        return embed, False
 
     @staticmethod
     def _predicate(
@@ -119,7 +122,10 @@ async def _listen_for_refresh(
             try:
                 # The returned discord.Message object from discord.Message.edit is different from the current
                 # discord.Message object, so it must be reassigned to update properly
-                message = await message.edit(embed=self._build_topic_embed(message.channel.id, message.embeds[0].title))
+                embed, remove_reactions = self._build_topic_embed(message.channel.id, message.embeds[0].title)
+                message = await message.edit(embed=embed)
+                if remove_reactions:
+                    await message.clear_reaction("🔄")
             except discord.NotFound:
                 break
 
@@ -135,7 +141,7 @@ async def topic(self, ctx: commands.Context) -> None:
 
         Allows the refresh of a topic by pressing an emoji.
         """
-        message = await ctx.send(embed=self._build_topic_embed(ctx.channel.id, None))
+        message = await ctx.send(embed=self._build_topic_embed(ctx.channel.id, None)[0])
         self.bot.loop.create_task(self._listen_for_refresh(ctx.author, message))