As part of the max-width layout work (T246420), a `layout-max-width.less` file was created containing all the styles relevant to the max-width work along with a `VectorLayoutMaxWidth` feature flag to make the deployment less risky. While the feature flag is helpful in the short-term, it has a high carrying cost  and will be difficult to maintain in the long-term. The max-width design should just be part of the modern Vector experience (non-configurable) and the feature flag removed as soon as possible following the deploy.
=== Developer Notes
Most of these styles should be easy enough to merge into `layout.less` or `Sidebar.less`, but there are several pending questions:
1) Should the Less variables found in `layout-max-width.less` be moved to `layout.less` or to `variables.less`? I think @Volker_E was of the opinion that these should be part of `variables.less`.
2) Should the styles pertaining only to history and special pages be split into their own stylesheet and conditionally loaded or be part of `layout.less` (where they load on every page)?
3) Should the breakpoint media queries be moved to `layout.less` or is there a better place to put these?
=== Acceptance Criteria
 `VectorLayoutMaxWidth` config flag is removed.
 All styles currently found in `layout-max-width.less` are merged into or added to the default modern Vector stylesheets (e.g. `layout.less`, `Sidebar.less`, etc.) and `layout-max-width.less` is removed.