switched SkSL's temporary 'highfloat' type back to 'float'

Bug: skia:
Change-Id: If0debae7318b6b5b4a7cb85d458996a09931127e
Reviewed-on: https://skia-review.googlesource.com/48760
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
67 files changed