This reverts commit b67102b1.

Reason for revert: breaks ANGLE roll into Chromium
https://chromium-review.googlesource.com/c/chromium/src/+/1827833
https://ci.chromium.org/p/chromium/builders/try/fuchsia_arm64/391223
https://ci.chromium.org/p/chromium/builders/try/fuchsia_x64/390587

Original change's description:
> Disable swiftshader on Fuchsia
> 
> SwiftShader is not needed on Fuchsia because the platform is expected to
> provide Vulkan on all devices.
> 
> Bug: fuchsia:37278
> Change-Id: I96d49f51dbe473bd032ec966137f35d2df9b6884
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1822863
> Reviewed-by: Michael Spang <spang@chromium.org>
> Reviewed-by: Jamie Madill <jmadill@chromium.org>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>

TBR=spang@chromium.org,jmadill@chromium.org,sergeyu@chromium.org

Change-Id: I39dabd1cc8de3bbef2c9fe233270a21de3782900
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: fuchsia:37278
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1828317Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>