Remove "precision" from SkSL lexer

This wasn't even referenced by the parser.

Change-Id: Id6246c3909b7f2b499908a742bdd61f4918f023a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372119
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
5 files changed