Fix styling

Author: Claudio-Emmolo

tests/AdsPostParserTest.php

@@ -66,8 +66,8 @@
     $content = (new AdsPostParser($this->contentOnlyParagraphs))->appendAdvertising();
 
     expect($content)
-        ->toContain("<p>Paragraph1</p><div>--- YOUR AD1 HERE ---</div>")
-        ->toContain("<p>Paragraph4</p><div>--- YOUR AD2 HERE ---</div>");
+        ->toContain('<p>Paragraph1</p><div>--- YOUR AD1 HERE ---</div>')
+        ->toContain('<p>Paragraph4</p><div>--- YOUR AD2 HERE ---</div>');
 });
 
 it('can append first and second advertising', function () {