Lower gRPC server inactivity ping timeout
This change lowers the gRPC inactivity ping timeout from 2 hours to 20 seconds to improve the user experience after a potential silent network failure.
These pings will increase observability of network related failures at the expense of more network traffic.
Relates to #1718 (closed) and gitlab#28977 (closed)
Follow up issue: gitlab-workhorse#231 (closed)
Edited by GitLab Release Tools Bot