Roll Fuchsia SDK from 0.20200918.1.1 to 0.20200918.2.1

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-sdk-chromium-autoroll
Please CC cr-fuchsia+bot@chromium.org on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Cq-Include-Trybots: luci.chromium.try:fuchsia-arm64-cast;luci.chromium.try:fuchsia-x64-cast
Tbr: cr-fuchsia+bot@chromium.org
Change-Id: Ib49002b92910784299238b52019db57343b9ffaa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2419235Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#808466}

build/fuchsia/linux.sdk.sha1

-0.20200918.1.1
+0.20200918.2.1

build/fuchsia/mac.sdk.sha1

-0.20200918.0.1
+0.20200918.2.1