change python requirements to 3.6

Author: peiyun@inj21

setup.py

@@ -16,8 +16,8 @@
 URL = "https://github.com/InjectiveLabs/sdk-python"
 EMAIL = "[email protected]"
 AUTHOR = "Injective Labs"
-REQUIRES_PYTHON = ">=3.9.0"
-VERSION = "0.2.8"
+REQUIRES_PYTHON = ">=3.6.0"
+VERSION = "0.3.0"
 
 REQUIRED = [
     "grpcio",