Remove support for version 2021-01,04

Author: mllemango

CHANGELOG

@@ -1,5 +1,6 @@
 == Unreleased
-- Update API version with 2022-04 release, remove API version 2020-10
+- Update API version with 2022-04 release
+- remove API version 2020-10, 2021-01, 2021-04 as they are all unsupported as of 2022-04
 
 == Version 10.0.0
 - Update API version with 2022-01 release, remove API version 2020-07

shopify/api_version.py

@@ -27,8 +27,6 @@ def define_version(cls, version):
     @classmethod
     def define_known_versions(cls):
         cls.define_version(Unstable())
-        cls.define_version(Release("2021-01"))
-        cls.define_version(Release("2021-04"))
         cls.define_version(Release("2021-07"))
         cls.define_version(Release("2021-10"))
         cls.define_version(Release("2022-01"))