Fix "box" character in JPM repo view on Windows

The default font (Segoe UI) doesn't have symbol characters so the down
arrow next to a bundle/rev is just a box.

In the RepositoriesView swap it with an icon instead.

Signed-off-by: Sean Bright <sean@malleable.com>
Merge pull request #893 from seanbright/jpm-repo-view-box-chars

Fix "box" character in JPM repo view on Windows