Problematic fix for font boosting

JDK-8277420 included the addition to the stylesheet shown below to prevent font boosting aka text inflation in mobile browsers.

/* Disable font boosting */
h1, h2, h3, h4, h5, h6 {
    max-height: 2em;
}

This was necessary because otherwise the font size of headings would change depending on whether the copy-to-clipboard icon was visible or not.

Unfortunately there are several issues with this change. While the definition of a `max-height` property for header elements prevents font-boosting, the value of 2em is too small for headers which require multiple line breaks. This can be seen in the attached screenshot where the header overlaps the following text.

At the same time, font boosting is a problem that is not only present in header elements. In fact it is also visible in constructor and method signatures in member details and, less apparent, other parts of the generated documentation.

Considering all of the above we should add a CSS declaration that applies to all elements with a `max-height` value that is beyond any reasonable value. It is unfortunate that the `max-height` hack is the only thing that works. There is a `text-size-adjust` CSS property proposed for this purpose as well as several browser-specific variants of it, but unfortunately it doesn't yet work for Chrome on Android which is the biggest offender.