Update composer.json

Author: mianzaid

composer.json

@@ -43,8 +43,7 @@
 		"guzzlehttp/psr7": "~1.1 || ^2.0"
 	},
 	"require-dev": {
-		"phpunit/phpunit": "^4.8 || ^5.7 || ^7.5.15",
-		"mockery/mockery": "~0.9.2"
+		"phpunit/phpunit": "^4.8 || ^5.7 || ^7.5.15"
 	},
 	"suggest": {
 		"ext-gd": "to use GD library based image processing."