Remove SkSurface::MakeFromBackendTextureAsRenderTarget variant that doesn't take SkColorType

Bug: skia:6718
Change-Id: I3fabe2050394bfbd8ad2fa600d07323838308ae5
Reviewed-on: https://skia-review.googlesource.com/115087
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed