Deploy button re-enables after deploying, following removal of unused page via Configuration Nodes menu

### Current Behavior

If a ui-page, other than the last page, is emptied and then removed using menu > Configuration Nodes while the Dashboard pane is not visible in the editor, and then Deployed, then later (even after node-red restart) if the dashboard pane is shown then the Deploy button becomes re-enabled.
This can be confusing for the user as it may not happen until hours or days after the page is removed - suddenly without warning the Deploy button becomes enabled and refreshing the browser or restarting node-red does not make it go away.

What appears to be happening is that removing the page via the menus does not update the page order fields in the configuration, then when the Dashboard pane is opened it notices the missing page and re-orders them, so forcing a Deploy requirement. I suspect the same thing may happen with groups and possibly Spacer nodes, though I have not tested that.

### Expected Behavior

No re-deploy should be necessary.

### Steps To Reproduce

1. Select the Help pane on the right hand side
2. Empty a page other than the last one
3. Use the menu item Configuration Nodes > unused and delete the empty groups and page.
4. Deploy
5. Show the Dashboard pane
6. The Deploy button is enabled again.

Inspecting the differences in the flow file shows that the order fields in the page have been updated, causing the deploy button to be enabled again.

### Environment

- Dashboard version: 1.31.0 (and earlier)
- Node-RED version: 1.4.1
- Node.js version:
- npm version:
- Platform/OS:
- Browser:

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate