Remove dead _resolvePackageUri implementation

The implementation for `Isolate.resolvePackageUri` is entirely within
`isolate_patch.dart`.

https://github.com/dart-lang/sdk/blob/b080e7c97a879eb803c725621b3993cbe994d19d/sdk/lib/_internal/js_runtime/lib/isolate_patch.dart#L33-L40

Change-Id: Ic2872369154f85814815d56b89ccc227af5434ad
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/104602
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Nate Bosch <nbosch@google.com>
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index d0a1215..5fc220c 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -740,15 +740,6 @@
   }
 }
 
-Uri _resolvePackageUri(Uri packageUri) {
-  assert(packageUri.scheme == "package");
-  if (packageUri.hasAuthority) {
-    throw new ArgumentError("Package-URI must not have a host: $packageUri");
-  }
-  var resolved = Uri.base.resolve("packages/${packageUri.path}");
-  return resolved;
-}
-
 bool _hasErrorStackProperty = JS('bool', 'new Error().stack != void 0');
 
 @patch