Roll Fuchsia SDK from 27.20250419.0.1 to 27.20250421.4.1

If this roll has caused a breakage, revert this CL and stop the roller
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https://autoroll.skia.org/r/fuchsia-sdk-dart-sdk
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is aware of the problem.

To file a bug in Fuchsia SDK: https://bugs.fuchsia.dev/p/fuchsia/issues/list
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Cq-Include-Trybots: luci.dart.try:vm-fuchsia-release-x64-try;luci.dart.try:vm-fuchsia-release-arm64-try
Change-Id: I34abe6e3db09d7f77154d265be398af868cda7ca
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/423540
Reviewed-by: Derek Xu <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>
Reviewed-by: Ryan Macnak <[email protected]>

Author: DEPS Autoroller

DEPS

@@ -85,7 +85,7 @@ vars = {
   "download_reclient": True,
 
   # Update from https://chrome-infra-packages.appspot.com/p/fuchsia/sdk/core
-  "fuchsia_sdk_version": "version:27.20250419.0.1",
+  "fuchsia_sdk_version": "version:27.20250421.4.1",
   "download_fuchsia_deps": False,
 
   # Ninja, runs the build based on files generated by GN.