Remove unused $valueList parameter from Stylesheet

Remove unused `$valueList` paramenter from
`Concrete\Core\StyleCustomizer\Stylesheet`

`$valueList` appears to have become a class property now as opposed to
being passed in as a parameter. The parameter does not appear to be used
in the method and a scan for other `getCSS()` calls shows them as also
not using the parameter.
PSR-2 Formatting
Merge pull request #1233 from mkly/remove_leftover_parameter

Remove unused $valueList parameter from Stylesheet