Revert "add BoardConfig flag TARGET_USES_OPENGLES_FOR_SCREEN_CAPTURE"

This reverts commit 717dfec6a6fb750823495e8d2f7d3f62c4d95039.
sf: Always use opengles for screen capture

Go back to the usage of GRALLOC_USAGE_HW_TEXTURE and GRALLOC_USAGE_HW_RENDERER
in captureScreenImplLocked regardless of useReadPixels value

This fixes the EGL_NO_IMAGE_KHR error returned from
eglCreateImageKHR (blank images returned from screenshot path)

Change-Id: I62fe90a081607b9e89c67f3dcfd34c84efc89d35