Fix bug in CSS tokenizer (#3906)

... causing a rogue "closing tag" token being inserted, which leads to problematic output when a fixer tries to manipulate the token.

Includes test via the sniff which led to discovery of the issue.

src/Standards/Squiz/Tests/WhiteSpace/SuperfluousWhitespaceUnitTest.1.css

@@ -23,3 +23,10 @@
 }
 /* phpcs:set Squiz.WhiteSpace.SuperfluousWhitespace ignoreBlankLines false */
 
+// /**
+//  * This text is in two types of comment: each line is commented out
+//  * individually, and the whole block is in what looks like a
+//  * docblock-comment. This sniff should ignore all this text as there
+//  * is no superfluous white-space here.
+//  */
+

src/Standards/Squiz/Tests/WhiteSpace/SuperfluousWhitespaceUnitTest.1.css.fixed

@@ -21,3 +21,10 @@
     float: left;
 }
 /* phpcs:set Squiz.WhiteSpace.SuperfluousWhitespace ignoreBlankLines false */
+
+// /**
+//  * This text is in two types of comment: each line is commented out
+//  * individually, and the whole block is in what looks like a
+//  * docblock-comment. This sniff should ignore all this text as there
+//  * is no superfluous white-space here.
+//  */

src/Standards/Squiz/Tests/WhiteSpace/SuperfluousWhitespaceUnitTest.php

@@ -84,7 +84,7 @@ public function getErrorList($testFile='SuperfluousWhitespaceUnitTest.inc')
                 8  => 1,
                 9  => 1,
                 11 => 1,
-                25 => 1,
+                32 => 1,
             ];
             break;
         default:

src/Tokenizers/CSS.php

@@ -196,7 +196,11 @@ public function tokenize($string)
 
                 // The first and last tokens are the open/close tags.
                 array_shift($commentTokens);
-                array_pop($commentTokens);
+                $closeTag = array_pop($commentTokens);
+
+                while ($closeTag['content'] !== '?'.'>') {
+                    $closeTag = array_pop($commentTokens);
+                }
 
                 if ($leadingZero === true) {
                     $commentTokens[0]['content'] = substr($commentTokens[0]['content'], 1);