[TabGroups] Update histogram expiry dates

Bumps the following histograms from 2025-05-xx to 2025-10-xx:
- TabGroups.SavedTabGroupTabTimeSinceModification
- TabGroups.SavedTabGroupTimeSinceModification
- TabGroups.Shared.GroupDeleted
- TabGroups.Shared.TabGroupAge
- TabGroups.Shared.TotalTabGroupCount
- TabGroups.Shared.TotalTabGroupTabCount

These metrics will continue to be in use until a little after the
shared tab groups feature has launched. After that time we can
reevalutate if these metrics will continue to be recorded or removed.

Change-Id: I2e939f70ef2dd5acbfecbe29a891b4bb29ce727b
Bug: 407543230
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6438586
Reviewed-by: Daniel Soromou <koretadaniel@chromium.org>
Reviewed-by: Caroline Rising <corising@chromium.org>
Commit-Queue: Darryl James <dljames@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1443649}