Use <span> for course preview’s university

The course’s university was displayed using a <a> tag that points to
nothing ('#'). There was some stanford specific behavior to replace that
<a> tag with a <span>. This commit removes that.

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I couldn’t find any code relying on the `<a>` tag to be present.
Having a `<a>` tag here breaks the layout, displays the university and the start date on two different lines (caused by https://github.com/tusbar/edx-platform/blob/course-bottom-university-span/lms/static/sass/shared/_course_object.scss#L71)

Another option would be to add `display: inline` to https://github.com/tusbar/edx-platform/blob/course-bottom-university-span/lms/static/sass/shared/_course_object.scss#L228