Adjust sizing of page header links on mobile viewports

[joedolson]

In #41986, the styling of the page title actions was adjusted to match the global button style. However, this styling was not also applied to the mobile viewport, and the mobile version does not match; it has excessive height, in particular.

This will require change the padding to 0 14px, adding min-height of 40px, lilne-height of 2.71428571, and vertical-align middle in the mobile viewport.

Attributing this to 6.4, as that's the point where it should have been adjusted, though the styles themselves are considerably older.

Trac ticket: https://core.trac.wordpress.org/ticket/63831

[joedolson]

Before

[joedolson]

After

[joedolson]

I reversed the labels on those images. The first is after, the second is before.