Disable ServiceProcessControlBrowserTest.LaunchAndReconnect on macOS

The test is flaky.

Bug: 978948
Change-Id: Ie875f58d995d2b0b4fa816bed47eeb9da86eb266
Tbr: thestig@chromium.org
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1678849
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672605}