[5.1] WebAssetManager: reset sorting state when new item enabled or disabled

[Fedik]

Summary of Changes

WebAsset ignoring newly added assets (without dependencies) after https://github.com/joomla/joomla-cms/pull/42661 This PR is fixing it.

Testing Instructions

Apply patch, visit home page, and check for Schema.org markup in source code.

Actual result BEFORE applying this Pull Request

None (except BreadcrumbList)

Expected result AFTER applying this Pull Request

It is there

Link to documentations

Please select:

• [ ] Documentation link for docs.joomla.org:
• [x] No documentation changes for docs.joomla.org needed
• [ ] Pull Request link for manual.joomla.org:
• [x] No documentation changes for manual.joomla.org needed