Update requerements and add python 3.10 support

cogs/utils/dict_utils.py

@@ -11,7 +11,7 @@ def flatten(d, parent_key='', sep='/'):
     items = []
     for k, v in d.items():
         new_key = parent_key + sep + k if parent_key else k
-        if isinstance(v, collections.MutableMapping):
+        if isinstance(v, collections.abc.MutableMapping):
             items.extend(flatten(v, new_key, sep=sep).items())
         else:
             items.append((new_key, v))

requirements.txt

@@ -1,5 +1,5 @@
 discord.py == 1.7.*
-git+https://github.com/Devoxin/Lavalink.py@dev
+lavalink
 asyncio
 pyyaml
 BeautifulSoup4