branding/logo/shirt-logo.svg: Adjust bounding box for tight fit

There's no reason to claim a few hundred extra pixels of empty space
in either dimension.  A tighter fit makes it easy to place this in a
slide without crowding out the other content.
Merge pull request #51 from wking/shirt-logo-bounding-box

media/src/vector/SWC-logo.svg: Adjust bounding box for tight fit