Remove CompilationUnitElementImpl.replaceTopLevelVariable

Change-Id: I598fff647524fb8c6737d4eeed9ca9d0fc863913
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/123623
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

pkg/analyzer/lib/src/dart/element/element.dart

@@ -1665,14 +1665,6 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
     return getTypeFromTypes(className, types);
   }
 
-  /// Replace the given [from] top-level variable with [to] in this compilation
-  /// unit.
-  void replaceTopLevelVariable(
-      TopLevelVariableElement from, TopLevelVariableElement to) {
-    int index = _variables.indexOf(from);
-    _variables[index] = to;
-  }
-
   @override
   void visitChildren(ElementVisitor visitor) {
     super.visitChildren(visitor);