Correct codefix by removing private modifier

In case of private attribute and private constructor parameter with
assignment in the constructor body, the parameter is flagged as unused.
This is caused by the private modifier which is shadowed by the
explicity assignment in the body.
This commit updates the codefix to just remove the private modifier in
this cases.

Closes #24931

Author: KnisterPeter

src/services/codefixes/fixUnusedIdentifier.ts

@@ -200,8 +200,14 @@ namespace ts.codefix {
 
     function tryDeleteParameter(changes: textChanges.ChangeTracker, sourceFile: SourceFile, p: ParameterDeclaration, checker: TypeChecker, sourceFiles: ReadonlyArray<SourceFile>, isFixAll: boolean): void {
         if (mayDeleteParameter(p, checker, isFixAll)) {
-            changes.delete(sourceFile, p);
-            deleteUnusedArguments(changes, sourceFile, p, sourceFiles, checker);
+            const privateModifier = ts.findModifier(p, ts.SyntaxKind.PrivateKeyword);
+            if (privateModifier) {
+                changes.deleteModifier(sourceFile, p.modifiers![0]);
+            }
+            else {
+                changes.delete(sourceFile, p);
+                deleteUnusedArguments(changes, sourceFile, p, sourceFiles, checker);
+            }
         }
     }