docs: Update argocd-cm.yaml bannerposition description (#16961) (#16962)

Signed-off-by: Keith Chong <kykchong@redhat.com>

docs/operator-manual/argocd-cm.yaml

@@ -308,8 +308,10 @@ data:
   # have either a permanent banner or a regular closeable banner, and NOT both. eg. A user can't dismiss a
   # notification message (closeable) banner, to then immediately see a permanent banner.
   # ui.bannerpermanent: "true"
-  # An option to specify the position of the banner, either the top or bottom of the page. The default is at the top.
-  # Uncomment to make the banner appear at the bottom of the page. Any value other than "bottom" will make the banner appear at the top.
+  # An option to specify the position of the banner, either the top or bottom of the page, or both. The valid values 
+  # are: "top", "bottom" and "both".  The default (if the option is not provided), is "top". If "both" is specified, then 
+  # the content appears both at the top and the bottom of the page. Uncomment the following line to make the banner appear 
+  # at the bottom of the page. Change the value as needed.
   # ui.bannerposition: "bottom"
 
   # Application reconciliation timeout is the max amount of time required to discover if a new manifests version got