Roll Fuchsia SDK from 6.20210929.0.1 to 6.20210929.2.1

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
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is aware of the problem.

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

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Change-Id: I3c293be361b4317b70303414de2bec173a031a08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3194674
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build/fuchsia/linux.sdk.sha1

@@ -1 +1 @@
-6.20210929.0.1
+6.20210929.2.1

build/fuchsia/mac.sdk.sha1

@@ -1 +1 @@
-6.20210929.1.1
+6.20210929.2.1