Remove List.copyFrom from VM and from tests. It was removed from the List interface in r941.

lib/html/src/DocumentFragmentWrappingImplementation.dart

Index: lib/html/src/DocumentFragmentWrappingImplementation.dart
diff --git a/lib/html/src/DocumentFragmentWrappingImplementation.dart b/lib/html/src/DocumentFragmentWrappingImplementation.dart
index 6fd883b40c559058002c3cda2cc760b78d90d3b4..90b3a404ba8256f9379ca2c83fc7da9afa74686f 100644
--- a/lib/html/src/DocumentFragmentWrappingImplementation.dart
+++ b/lib/html/src/DocumentFragmentWrappingImplementation.dart
@@ -60,10 +60,6 @@ class FilteredElementList implements ElementList {
     throw const UnsupportedOperationException('TODO(jacobr): should we impl?');
   }
 
-  void copyFrom(List<Object> src, int srcStart, int dstStart, int count) {
-    throw const NotImplementedException();
-  }
-
   void setRange(int start, int length, List from, [int startFrom = 0]) {
     throw const NotImplementedException();
   }