[tc] welcoming Mohammed Naser as our new TC chair for Train

Everyone, As I mentioned in a previous email, I decided to step down as TC chair this cycle. Mohammed Naser has volunteered to serve as chair for the Train cycle, and was confirmed by the committee during our meeting today [1]. We have one or two more bookkeeping items to take care of in the transition, but agreed that Mohammed would start serving as chair right away. Thank you, Mohammed, for volunteering. I wish I knew where you found the time to do all that you do for our community! -- Doug [1] https://review.openstack.org/#/c/641405/