[Files app] Added fdegros to OWNERS

Change-Id: If9612d3e9bd7dad163fdadfa65b37a3e82e1cc21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1609724
Auto-Submit: François Degros <fdegros@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659377}

ui/file_manager/OWNERS

 amistry@chromium.org
 dats@chromium.org
+fdegros@chromium.org
 fukino@chromium.org
 joelhockey@chromium.org
 lucmult@chromium.org