demos: high_res: Change "About" to "Security" and update TI logo

1. The tab that says "About" leads to a screen that shows a presentation
   on Security. So change the title and logos of the tab to "Security".
2. Update TI logo, so that it works with both light and dark modes.

Signed-off-by: Suhaas Joshi <s-joshi@ti.com>

Author: jsuhaas22