Clarify error message for instantiating abstract classes

Fixes #38695

Consistent with terminology in https://dart.dev/guides/language/language-tour#abstract-classes

Closes #38706
#38706

GitOrigin-RevId: 37eccff
Change-Id: Ia9434b8b7957f1009fe1d987cbcf5bf878ba540b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/119880
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

Author: mit-mit

pkg/analyzer/lib/src/error/codes.dart

@@ -6439,7 +6439,7 @@ class StaticWarningCode extends AnalyzerErrorCode {
    */
   static const StaticWarningCode NEW_WITH_ABSTRACT_CLASS =
       const StaticWarningCode('NEW_WITH_ABSTRACT_CLASS',
-          "Abstract classes can't be created with a 'new' expression.",
+          "Abstract classes can't be instantiated.",
           correction: "Try creating an instance of a subtype.");
 
   /**