Replace a couple of `assert(3)` calls.

Change-Id: I75197c63c4ffb7152c91524f567c5b14599a43ad
Reviewed-on: https://code-review.googlesource.com/c/re2/+/62170
Reviewed-by: Alex Chernyakhovsky <achernya@google.com>
Reviewed-by: Paul Wankadia <junyer@google.com>
1 file changed