Bump minimum mautrix-python version

requirements.txt

@@ -4,5 +4,5 @@ commonmark>=0.8,<0.10
 aiohttp>=3,<4
 yarl>=1,<2
 attrs>=19.1
-mautrix>=0.14.0rc4,<0.15
+mautrix>=0.14.1,<0.15
 asyncpg>=0.20,<0.26