Adjust layout for Create Vulnerability button on mobile view

The following discussion from !87040 (merged) should be addressed:

• @dftian started a discussion: (+1 comment)

While this fixes the button's height, it does feel somewhat weird that we keep the title and actions side-by-side on mobile. I believe that we usually adjust the layout so that actions are moved below the title on smaller viewports. That's what we did for on-demand scans for example:

Desktop	Mobile