docs(dotnet): library-csharp.md - use new() syntax everywhere (#16666)

docs(library-csharp.md): use new() syntax everywhere

docs/src/library-csharp.md

@@ -34,7 +34,10 @@ using var playwright = await Playwright.CreateAsync();
 await using var browser = await playwright.Chromium.LaunchAsync();
 var page = await browser.NewPageAsync();
 await page.GotoAsync("https://playwright.dev/dotnet");
-await page.ScreenshotAsync(new PageScreenshotOptions { Path = "screenshot.png" });
+await page.ScreenshotAsync(new()
+{
+    Path = "screenshot.png"
+});
 ```
 
 Now run it.