Remove half float workaround in GrGLGpu::onReadPixels

To ensure that SwiftShader keeps working, always read
back F16 as F32 on GL.

Bug: skia:
Change-Id: I0d4184a3e9072a6f4cbc7533ddda658ac76f7f84
Reviewed-on: https://skia-review.googlesource.com/138585
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
2 files changed