Anchor link offset fix is not working properly in Chrome

MDL-71152 introduce scroll-margin-top to scroll to an element when its anchor is set in the URL. It works properly on Firefox, Safari, Edge.

In Chrome it mostly does, except when the anchor in the URL is the first block on the main content area of the Dashboard (Recently accessed courses in a fresh instance).

The anchor link offset fix styles are located in theme/boost/scss/moodle/drawer.scss. Consider if that is the ideal place.

Example:

• Login and access the dashboard using Chrome
• With the inspector look for the id (instNN) of the block on the main content area (usually Recently accessed courses)
• Add "#instNN" to the browser URL and press enter
• Check that page scrolls to the block but it is partially hidden by the fixed header.