docs: document when-then + migrations revert change (#8089)

- Add documentation around when-then and workflow conditions
- Change the CLI reference based on change in revert migrations command.

www/apps/book/sidebar.mjs

@@ -191,6 +191,10 @@ export const sidebar = sidebarAttachHrefCommonOptions(
               path: "/advanced-development/workflows/constructor-constraints",
               title: "Workflow Constraints",
             },
+            {
+              path: "/advanced-development/workflows/conditions",
+              title: "Conditions in Workflows",
+            },
             {
               path: "/advanced-development/workflows/compensation-function",
               title: "Compensation Function",