The `map` class is applied to the map element by LeafletJS; using it in
the container led to hacks like adding an `inline` class to fix the fact
that the container was using the `height` rule of the `.map` elements.
Even though we don't add styles for them, I'm adding the `budgets-map`
and `budget-investments-map` HTML classes so these elements can still be
easily selected with CSS and JavaScript.
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