TwentyTwenty modal admin bar offset is targeting wrong class

[schlessera]

Bug Description

The TwentyTwenty theme compat code needs to add a CSS offset to a modals when the admin bar is shown, so that they are not partially obscured by the admin bar.

The current code targets a specific modal, though (.menu-modal), instead of all modals (.cover-modal).

This causes the search modal to be stuck behind the admin bar still.

Expected Behaviour

All modals should be offset to account for the admin bar.

Steps to reproduce

1. Open a twentytwenty-themed site at any AMP URL.
2. Click on the magnifying glass in the header bar to open the search modal.

Screenshots

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[csossi]

Verified in QA: