Update gast requirement, test=develop (#30932)

gast version can be conflict with the other software users installed. We set the version to be higher than 0.3.3

python/requirements.txt

@@ -3,7 +3,7 @@ numpy>=1.13, <=1.16.4 ; python_version<"3.5"
 numpy>=1.13 ; python_version>="3.5" and platform_system != "Windows"
 numpy>=1.13, <=1.19.3 ; python_version>="3.5" and platform_system == "Windows"
 protobuf>=3.1.0
-gast==0.3.3
+gast>=0.3.3
 Pillow
 six
 decorator