fix(docs-infra): fix layout of `file-not-found` page (#31390)
fix(docs-infra): fix layout of `file-not-found` page (#31390)

The `.sidenav-content` element, [which is also][1] the `#file-not-found`
element, [already has][2] the necessary padding. Especially the top
padding is important to ensure the element is not obscured by the
top-bar.

[1]: https://github.com/angular/angular/blob/1d3e22766/aio/src/app/app.component.html#L51
[2]: https://github.com/angular/angular/blob/1d3e22766/aio/src/styles/1-layouts/_content-layout.scss#L10

PR Close #31390

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