Roll Fuchsia Mac SDK from zC90VpkAGMG1jJ-BK... to 6xysoRPCXJ3cJX12x... (flutter/engine#38746)

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

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DEPS

@@ -816,7 +816,7 @@ deps = {
      'packages': [
        {
         'package': 'fuchsia/sdk/core/mac-amd64',
-        'version': 'zC90VpkAGMG1jJ-BKmFqF8gWp4vYu6FGaFAwUXf9QWMC'
+        'version': '6xysoRPCXJ3cJX12x2Z-uYCsDxak4cGAcywM84p3TSkC'
        }
      ],
      'condition': 'host_os == "mac" and not download_fuchsia_sdk',