Capture/Replay Tests: Allow 3 concurrent ninja processes. This is an attempt to fix the flaky ninja error when running multiple processes while still getting pretty good test times. The previous fix eliminated the flakiness but doubled the test time. In local testing this is a bit slower but not 2x slower. Bug: angleproject:6299 Change-Id: Ibcd462712d3eab759c5923ca229e009046783e9b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3149570 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>