pin pyyaml to v6.0.1 (#326)

* fixes #324

Author: BenjiU

pyproject.toml

@@ -9,7 +9,7 @@ documentation = "https://flyte.github.io/mqtt-io/"
 
 [tool.poetry.dependencies]
 python = "^3.6"
-PyYAML = "^6.0"
+PyYAML = "^6.0.1"
 Cerberus = "^1.3.2"
 typing-extensions = "^3.7.4"
 dataclasses = { version = "^0.8", python = ">=3.6,<3.7" }