Updater: Clarify user counting docs.

There was a logical inversion in the section ("greater
 than or equal to" instead of "less than"), and it was
overly wordy.

Change-Id: Idbfd7ec1781318ebdc4b0f29ca29235a90cbb7c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3448429


Auto-Submit: Joshua Pawlicki <waffles@chromium.org>
Reviewed-by: Sorin Jianu <sorin@chromium.org>
Commit-Queue: Sorin Jianu <sorin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#968361}