SkQP: remove model slack, README

Change-Id: Ifd258ccd633fba11a13ac3ffc92fb684789d3e57
Reviewed-on: https://skia-review.googlesource.com/102205
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
2 files changed