typo: patter -> pattern in lib/core/pattern.dart
typo: patter -> pattern in lib/core/pattern.dart

Closes https://github.com/dart-lang/sdk/pull/47198
https://github.com/dart-lang/sdk/pull/47198

GitOrigin-RevId: 647929b9ed24826261d37f60bd2180d79917e954
Change-Id: Ic857fffa8232e29f8ae5248bc7c4ce9264a090b5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/213220
Reviewed-by: Kevin Moore <1d6e7d10d051cf619c5282da3c28fd8d3e0a65a4@google.com>
Commit-Queue: Kevin Moore <1d6e7d10d051cf619c5282da3c28fd8d3e0a65a4@google.com>

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