Remove precision from GrGLSLVaryingHandler

(It's built into the types now.)

Bug: skia:
Change-Id: I44edc6e71098cf74387091903e920b1dd929b103
Reviewed-on: https://skia-review.googlesource.com/59880
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
18 files changed