Requirements: fix typo

Author: jrfnl

wiki/Requirements.md

@@ -1,6 +1,6 @@
 PHP_CodeSniffer requires PHP version 5.4.0 or greater, although individual sniffs may have additional requirements such as external applications and scripts. See the [[Configuration Options]] manual page for a list of these requirements.
 
 Additionally, PHP_CodeSniffer requires the following PHP extensions to be enabled:
-- Tokenizer: used by the core tokenzier to process PHP files
+- Tokenizer: used by the core tokenizer to process PHP files
 - SimpleXML: used to process ruleset XML files
 - XMLWriter: used to create some report formats