[parser] Update comments for primary constructor listeners.

Small PR to just update some comments that changed after Johnni's parser
CL https://dart-review.googlesource.com/c/sdk/+/455081

These two listener methods are called for enums, classes and extension
types, not for only extension types.

Bug: #61699
Change-Id: I9935bdb071b01179d59d96a65fd3b675d3c4cfe4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/457521
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Kallen Tu <[email protected]>

Author: kallentu

pkg/_fe_analyzer_shared/lib/src/parser/listener.dart

@@ -315,8 +315,7 @@ abstract class Listener implements UnescapeErrorListener {
     logEvent('ExtensionTypeDeclaration');
   }
 
-  /// Handle the start of a primary constructor declaration, currently only
-  /// occurring in extension type declarations.
+  /// Handle the start of a primary constructor declaration.
   void beginPrimaryConstructor(Token beginToken) {
     logEvent('PrimaryConstructor');
   }
@@ -340,8 +339,7 @@ abstract class Listener implements UnescapeErrorListener {
     logEvent('PrimaryConstructor');
   }
 
-  /// Handle the omission of a primary constructor declaration. Currently only
-  /// occurring in extension type declarations.
+  /// Handle the omission of a primary constructor declaration.
   void handleNoPrimaryConstructor(
     Token token,
     Token? constKeyword,