Switch back docs version to master

Author: koic

docs/antora.yml

@@ -2,6 +2,6 @@ name: rubocop-performance
 title: RuboCop Performance
 # We always provide version without patch here (e.g. 1.1),
 # as patch versions should not appear in the docs.
-version: '1.20'
+version: ~
 nav:
   - modules/ROOT/nav.adoc