Unify branch names for odh-manifests and notebooks

Notebooks branch can be set explicitly via --notebooks-branch

Signed-off-by: Andrej Podhradsky <apodhrad@redhat.com>

rhods-disconnected-helper.sh

@@ -8,7 +8,7 @@ set_defaults() {
   rhods_version="${rhods_version:-}"
   repository_folder="${repository_folder:-.odh-manifests}"
   notebooks_folder="${notebooks_folder:-.odh-notebooks}"
-  notebooks_branch="${notebooks_branch:-release-2023a}"
+  notebooks_branch="${notebooks_branch:-}"
   file_name="${file_name:-$rhods_version.md}"
   skip_tls="${skip_tls:-false}"
   mirror_url="${mirror_url:-registry.example.com:5000/mirror/oc-mirror-metadata}"
@@ -186,6 +186,13 @@ function change_rhods_version() {
     echo "Error: Version $rhods_version does not exist"
     exit 1
   fi
+
+  # Set the same vesrion for notebooks if not set otherwise via
+  #   --notebooks-branch <notebooks_branch>
+  if [ -z "${notebooks_branch}" ]; then
+    notebooks_branch="${rhods_version}"
+  fi
+
   echo "Switching to $rhods_version"
   git switch "$rhods_version"
   return 0
@@ -244,6 +251,11 @@ parse_args() {
       shift
       shift
       ;;
+    --notebooks-branch)
+      notebooks_branch="$2"
+      shift
+      shift
+      ;;
     --skip-image-verification)
       skip_image_verification=true
       shift