[Form] Fixed StringUtil::trim() to trim ZERO WIDTH SPACE (U+200B) and SOFT HYPHEN (U+00AD)

src/Symfony/Component/Form/Tests/Util/StringUtilTest.php

@@ -72,7 +72,9 @@ class StringUtilTest extends TestCase
             ['000D'],
             ['0085'],
             // zero width space
-//            ['200B'],
+            ['200B'],
+            // soft hyphen
+            ['00AD'],
         ];
     }
 

src/Symfony/Component/Form/Util/StringUtil.php

@@ -33,7 +33,7 @@ class StringUtil
      */
     public static function trim($string)
     {
-        if (null !== $result = @preg_replace('/^[\pZ\p{Cc}]+|[\pZ\p{Cc}]+$/u', '', $string)) {
+        if (null !== $result = @preg_replace('/^[\pZ\pC]+|[\pZ\pC]+$/u', '', $string)) {
             return $result;
         }