Update orchestra/testbench

Author: sebdesign

composer.json

@@ -14,7 +14,7 @@
     "require-dev": {
         "phpunit/phpunit": "~5.4|~6.0|~7.0",
         "mockery/mockery": "^0.9|^1.0",
-        "orchestra/testbench": "~3.3|~3.4|~3.5|~3.6|~3.7"
+        "orchestra/testbench": "~3.3|~3.4|~3.5|~3.6|~3.7|~3.8"
     },
     "autoload": {
         "files": [