Presentations page: Merge duplicate entries for git-repo-metrics plugin talk

The link to the video had been added by change If1b06aa69, afterwards
change Id7ddfd198 added the links to the slides, but at a different
place.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I77bc2d4aa95add52add560fa1903b72ff75910eb
1 file changed