Fix SVG logos not displayed without width/height attribute

[silvio2402]

This is a bug fix.

Summary

In the masthead styles I changed the max-height of the site logo to height to allow for displaying SVG logos that don't have explicit width or height attributes set, which were previously rendered with 0 height, making them invisible.

How This Change Will Affect Other Users

I have tried with multiple different combinations of logos and SVG attributes. This change won't affect the majority of users. However, users who have a smaller logo which wasn't bound by the max-width of 2rem will now have a slightly bigger logo (2rem height), and of course the bug fix will affect users who were affected by the bug.

Context

This PR is related to the issue #3845 I opened.