Fix supported versions in the README file.

Author: pdelboca

README.rst

@@ -25,13 +25,11 @@ https://docs.ckan.org/projects/ckanext-spatial/en/latest/
 Supported Versions
 ------------------
 
-ckanext-spatial >= 2.0.0 supports CKAN 2.9 and CKAN 2.10.
+ckanext-spatial is being developed and maintained for CKAN 2.10 and CKAN 2.11.
+
 Check the
 [tested enviroments](https://github.com/ckan/ckanext-spatial/blob/master/.github/workflows/test.yml)
-for more details.  
-
-For previous CKAN versions please use the v1.x tags.
-
+for more details.
 
 Community
 ---------