Remove obsolete reference to Flex lexer.

We use our own custom lexer now.

Change-Id: I6a2a408094ba37c2eef7092f5a5caa107938613b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/356476
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed