[TASK] Avoid heredoc in a test

This allows the testcase being autoformatted without breaking
the tests for PHP 7.2

https://www.php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc

Author: oliverklee

tests/ParserTest.php

@@ -570,11 +570,10 @@ public function selectorRemoval(): void
     public function comments(): void
     {
         $document = self::parsedStructureForFile('comments');
-        $expected = <<<EXPECTED
-@import url("some/url.css") screen;
-.foo, #bar {background-color: #000;}
-@media screen {#foo.bar {position: absolute;}}
-EXPECTED;
+
+        $expected = '@import url("some/url.css") screen;'
+            . "\n.foo, #bar {background-color: #000;}"
+            . "\n@media screen {#foo.bar {position: absolute;}}";
         self::assertSame($expected, $document->render());
     }