JFile - error fix "Cannot pass parameter 2 by reference" (#11952)

* Fix of an error "Only variables should be passed by reference"

If you pass a string to methods ````append```` or ````write````, you will have an error ````Only variables should be passed by reference````

* Update file.php

* Update file.php

libraries/joomla/filesystem/file.php

@@ -377,14 +377,14 @@ public static function read($filename, $incpath = false, $amount = 0, $chunksize
 	 * Write contents to a file
 	 *
 	 * @param   string   $file         The full file path
-	 * @param   string   &$buffer      The buffer to write
+	 * @param   string   $buffer       The buffer to write
 	 * @param   boolean  $use_streams  Use streams
 	 *
 	 * @return  boolean  True on success
 	 *
 	 * @since   11.1
 	 */
-	public static function write($file, &$buffer, $use_streams = false)
+	public static function write($file, $buffer, $use_streams = false)
 	{
 		@set_time_limit(ini_get('max_execution_time'));
 
@@ -443,14 +443,14 @@ public static function write($file, &$buffer, $use_streams = false)
 	 * Append contents to a file
 	 *
 	 * @param   string   $file         The full file path
-	 * @param   string   &$buffer      The buffer to write
+	 * @param   string   $buffer       The buffer to write
 	 * @param   boolean  $use_streams  Use streams
 	 *
 	 * @return  boolean  True on success
 	 *
 	 * @since   3.6.0
 	 */
-	public static function append($file, &$buffer, $use_streams = false)
+	public static function append($file, $buffer, $use_streams = false)
 	{
 		@set_time_limit(ini_get('max_execution_time'));