This partially reverts the following change:

60ec8f576 Vulkan: break dependency to the depthClamp feature

The feature is no longer necessary, and simplifies the usage of
utility shaders.

Bug: angleproject:2361
Change-Id: I1e87ac8d2517c5a3b50e3d0cddd55c852e0e3e7d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1555313
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>