Update mautrix-python

requirements.txt

@@ -3,7 +3,7 @@ python-magic>=0.4,<0.5
 commonmark>=0.8,<0.10
 aiohttp>=3,<4
 yarl>=1,<2
-mautrix>=0.20.5,<0.21
+mautrix>=0.20.6,<0.21
 tulir-telethon==1.37.0a1
 asyncpg>=0.20,<0.30
 mako>=1,<2