Fix test teardown in ProgramPipelineTest31. We were deleting objects in the test desctructor, which could cause crashes in TSAN. Bug: angleproject:7944 Change-Id: Ib9d4f236cc79bcb20c971feca86d053120440769 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4162557 Auto-Submit: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>