Update instructions for adding a collapsible section (elastic#3484)

A super minor fix to make the step generic and not UI dependant.

Relates to elastic#3214

Author: alaudazzi

explore-analyze/dashboards/arrange-panels.md

@@ -23,7 +23,7 @@ Organize your dashboard panels into collapsible sections to improve readability
 To add a collapsible section:
 
 1. Open the dashboard and make sure that you are in **Edit** mode.
-2. Select **Add panel** and select **Collapsible section**. The collapsible section is added at the end of the dashboard.
+2. Add a new panel and select **Collapsible section**. The collapsible section is added at the end of the dashboard.
 3. Optionally, edit the label of the section.
 4. Drag and drop any panels you want into the section.
    :::{tip}