Roll Fuchsia SDK from 5.20210612.2.1 to 5.20210612.3.1

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 chrome-fuchsia-gardener@grotations.appspotmail.com 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

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Tbr: chrome-fuchsia-gardener@grotations.appspotmail.com
Disable-Retries: true
Change-Id: Ia2f15a471a99910c3714fe2e499b0b6d4e1e6c54
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2958118
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Cr-Commit-Position: refs/heads/master@{#891930}

build/fuchsia/linux.sdk.sha1

@@ -1 +1 @@
-5.20210612.2.1
+5.20210612.3.1

build/fuchsia/mac.sdk.sha1

@@ -1 +1 @@
-5.20210612.2.1
+5.20210612.3.1