update logo SVG

[StephDriver]

The Birkbeck logo used has paths which weren't combined such that it looks poor quality. The SVG has since been updated (private link) and the newer version should also be used on Hourglass.

[joemull]

Here's the direct link to the latest file, which is included in templates as an SVG without the doctype line, so that it can be inlined in the served HTML with {% include %}: https://github.com/openlibhums/memory-alpha/blob/28bdf6096e1a2f50e2d15a1acf29b308e73104d5/themes/alpha/templates/svg/birkbeck-logo.svg