downgrade orchestra/testbench to support php 7.0 for test env (CI)

Author: aivis

composer.json

@@ -17,7 +17,7 @@
     "require-dev": {
         "phpunit/phpunit": "~7.0",
         "mockery/mockery": "^0.9.4",
-        "orchestra/testbench": "^3.7"
+        "orchestra/testbench": "^3.5"
     },
     "autoload": {
 		"psr-0": {