MQE-849: Upgrading MTF PHP version to 7.2

Author: okolesnyk

dev/tests/functional/composer.json

@@ -2,15 +2,9 @@
     "config": {
         "sort-packages": true
     },
-    "repositories": [
-        {
-            "type": "git",
-            "url": "https://github.com/magento/mtf.git"
-        }
-    ],
     "require": {
         "php": "7.0.2|~7.0.6|~7.1.0|~7.2.0",
-        "magento/mtf": "dev-develop-PhpUnit70",
+        "magento/mtf": "1.0.0-rc60",
         "allure-framework/allure-phpunit": "~1.2.0",
         "doctrine/annotations": "1.4.*",
         "phpunit/phpunit": "~6.5.0",