Update a comment in `DFA::WorkqToCachedState()`.

Thanks to Andrew Gallant for pointing this out and also for requesting
the restoration of a deleted comment that explained a very subtle bug.

Change-Id: I9fb56788a27a8bbd2948f9049bee4cc4cfc9cb10
Reviewed-on: https://code-review.googlesource.com/c/re2/+/61090
Reviewed-by: Paul Wankadia <junyer@google.com>
Reviewed-by: Alex Chernyakhovsky <achernya@google.com>
1 file changed