Hide the "large" diff warning on "very large" diffs

Summary:
Ref T13110. Ref T13130. When a revision is "large" (100 - 1000 files) we hide the actual textual changes by default. When it is "very large" (more than 1000 files) we hide all the changesets by default.

For "very large" diffs, we currently still show the "large" warning, which doesn't really make sense since there aren't any actual changesets.

When a diff is "very large", don't show the "large" warning.

Test Plan:

• Viewed a small diff (<100 files), saw no warnings.
• Viewed a large diff (100-1000 files), saw just the large warning.
• Viewed a very large diff (>1000 files).
  • Before: both "large" and "very large" help warnings.
  • After: just "very large" warnings.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13130, T13110

Differential Revision: https://secure.phabricator.com/D19416