### Description
The wordmark logo inside the mobile footer is unlabeled. It is also in an h2 element, which is unnecessary and makes the heading structure of the page less clear. This was observed using VO in Chrome and Safari, but this issue should be reproducible in all screen reader/OS combinations.
https://phabricator.wikimedia.org/F34586280
### Expected
- The logo inside the footer uses the `sitetitle` message.
- The logo is placed inside a div or another element instead of an h2 element
# QA
- Visit https://en.m.wikipedia.beta.wmflabs.org/wiki/Spain. Ensure that footer still has the text "Wikipedia".
- Visit https://patchdemo.wmflabs.org/wikis/1053c9ce83/w/index.php?title=Main_Page&mobileaction=toggle_view_mobile. Inspect the html of the footer 's logo. The `img` tag should have an `alt` attribute set. This `img` element should be inside a `div` element.