MDL-70300 lib: Upgrade php css parser to 8.3.1

lib/php-css-parser/CSSList/CSSList.php

@@ -61,6 +61,7 @@ abstract class CSSList implements Renderable, Commentable {
 				$oListItem->setComments($comments);
 				$oList->append($oListItem);
 			}
+			$oParserState->consumeWhiteSpace();
 		}
 		if(!$bIsRoot && !$bLenientParsing) {
 			throw new SourceException("Unexpected end of document", $oParserState->currentLine());
@@ -211,20 +212,6 @@ abstract class CSSList implements Renderable, Commentable {
 		array_splice($this->aContents, $iOffset, $iLength, $mReplacement);
 	}
 
-    /**
-     * Insert an item before its sibling.
-     *
-     * @param mixed $oItem The item.
-     * @param mixed $oSibling The sibling.
-     */
-    public function insert($oItem, $oSibling) {
-        $iIndex = array_search($oSibling, $this->aContents);
-        if ($iIndex === false) {
-            return $this->append($oItem);
-        }
-        array_splice($this->aContents, $iIndex, 0, array($oItem));
-    }
-
 	/**
 	 * Removes an item from the CSS list.
 	 * @param RuleSet|Import|Charset|CSSList $oItemToRemove May be a RuleSet (most likely a DeclarationBlock), a Import, a Charset or another CSSList (most likely a MediaQuery)
@@ -327,7 +314,7 @@ abstract class CSSList implements Renderable, Commentable {
 
 		return $sResult;
 	}
-
+	
 	/**
 	* Return true if the list can not be further outdented. Only important when rendering.
 	*/