PHPCSDev: account for new PHPCS backfill

PHPCS 3.5.0 will backfill the new PHP 7.4 `T_BAD_CHARACTER` token.

Refs:
* squizlabs/PHP_CodeSniffer@96f878f

Author: jrfnl

PHPCSDev/ruleset.xml

@@ -22,6 +22,7 @@
         <exclude name="PHPCompatibility.Constants.NewConstants.t_coalesceFound"/>
         <exclude name="PHPCompatibility.Constants.NewConstants.t_coalesce_equalFound"/>
         <exclude name="PHPCompatibility.Constants.NewConstants.t_yield_fromFound"/>
+        <exclude name="PHPCompatibility.Constants.NewConstants.t_bad_characterFound"/>
     </rule>