Make otf-font-awesome a required dependency

Description:

After installing swappy, the toolbox icons in app look broken (display weird UTF8 character).

Additional info:

• package version(s): 1.5.1-1
• config and/or log files: N/A
• link to upstream bug report, if any: N/A

Steps to reproduce:

1. Install swappy
2. Ensure otf-font-awesome is not installed
3. Start swappy with any picture, look at the toolbar in the drawer