travis: remove email notifications
travis: remove email notifications

Don’t spam mailing list with CI run results.

Signed-off-by: Matias Elo <62402263e8617147f0e4dd5b7f6f8ec67f2b3d2c@nokia.com>

OpenFastPath/ofp,OpenFastPath/ofp,OpenFastPath/ofp,OpenFastPath/ofp