[iOS] Extending MobileSignInPromo histograms to M87

Changing the expiration date of MobileSignInPromo histograms to M87.

Bug: 969999
Change-Id: I8fc3d944fe452311945c39e9a89a174d648a160f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649319
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669550}
1 file changed