R1:b7843da963e2

Don't expand folded timelines just because users went to any anchor whatsoever

Summary:
Ref T12970. See PHI43. Currently, the "Show Older Comments" link gets auto-clicked if the user visits **any** anchor. This is not correct.

Instead, only auto-click it if the user visits a numeric anchor. This fixes the behavior approximately 98% of the time. See T12970 for a followup on the remaining ambiguous cases.

Test Plan:
- Viewed a revision with some folded transactions and a "Show Older Comments" link.