Remove deprecated DartType.isStructurallyEqualTo

Change-Id: Ibf7ec9f5af9011a162c1db5080702fddbdd4f27c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/423601
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>

pkg/analyzer/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 8.0.0-dev
 * Remove deprecated element model V1.
+* Remove deprecated `DartType.isStructurallyEqualTo`.
 
 ## 7.4.1
 * Restore `InstanceElement.augmented` getter.

pkg/analyzer/api.txt

@@ -3877,7 +3877,6 @@ package:analyzer/dart/element/type.dart:
     acceptWithArgument (method: R Function<R, A>(TypeVisitorWithArgument<R, A>, A))
     asInstanceOf2 (method: InterfaceType? Function(InterfaceElement2), experimental)
     getDisplayString (method: String Function({bool withNullability}))
-    isStructurallyEqualTo (method: bool Function(DartType), deprecated)
   DynamicType (class extends Object implements DartType):
     new (constructor: DynamicType Function())
   FunctionType (class extends Object implements DartType):

pkg/analyzer/lib/dart/element/type.dart

@@ -180,14 +180,6 @@ abstract class DartType {
     @Deprecated('Only non-nullable by default mode is supported')
     bool withNullability = true,
   });
-
-  /// Determines whether this type is the same as [other].
-  ///
-  /// Deprecated: this getter is a part of the analyzer's private
-  /// implementation, and was exposed by accident (see
-  /// https://github.com/dart-lang/sdk/issues/59763). Please use `==` instead.
-  @Deprecated('Use `==` instead')
-  bool isStructurallyEqualTo(covariant DartType other);
 }
 
 /// The type `dynamic` is a type which is a supertype of all other types, just