Bump minimum mautrix-python version

requirements.txt

@@ -4,6 +4,6 @@ commonmark>=0.8,<0.10
 aiohttp>=3,<4
 yarl>=1,<2
 attrs>=19.1
-mautrix>=0.8,<0.9
+mautrix>=0.8.5,<0.9
 asyncpg>=0.20,<0.22
 pycryptodome>=3,<4