Remove direct dependency on squizlabs/codesniffer.

It gets pulled in by our custom coding standard, so let it decide what version of squiz we need.

Author: beporter

composer.json

@@ -11,7 +11,6 @@
     "require": {
         "phpunit/phpunit": "~4.1",
         "phpdocumentor/phpdocumentor": "~2.0",
-        "squizlabs/php_codesniffer": "~2.0",
         "loadsys/loadsys_codesniffer": "~3.0"
     },
     "config": {