Revert "Add private grpixelconfigs for alpha_8 and alpha_half"

This reverts commit 33d17cbb003975fff895954435183756f9893c17.

Reason for revert: broke intel bots

Original change's description:
> Add private grpixelconfigs for alpha_8 and alpha_half
> 
> Bug: skia:
> Change-Id: I5191b6e045aea2a5af2b305b5972ad1e638a7ace
> Reviewed-on: https://skia-review.googlesource.com/71763
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: I6fff9241f7878f1ec7fad2663df9922c9cd8f628
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/72180
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
14 files changed