[DOCS] Remove branches from Stack Overview (#1870)

Author: lcawl

conf.yaml

@@ -1955,10 +1955,9 @@ contents:
                 path:   shared/attributes.asciidoc
           - title:      Stack Overview
             prefix:     en/elastic-stack-overview
-            current:    *stackcurrent
+            current:    7.4
             index:      docs/en/stack/index.asciidoc
-            branches:   [ master, 7.x, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1, 7.0, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3 ]
-            live:       *stacklive
+            branches:   [ 7.4, 7.3, 7.2, 7.1, 7.0, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3 ]
             chunk:      1
             noindex:    1
             tags:       Legacy/Elastic Stack/Overview