Removed prophecy as required dependecy

Author: damianopetrungaro

composer.json

@@ -3,11 +3,11 @@
   "require": {
     "php": ">=7.1",
     "psr/http-message": "^1.0",
-    "http-interop/http-middleware": "^0.4.1",
-    "phpspec/prophecy": "^1.7"
+    "http-interop/http-middleware": "^0.4.1"
   },
   "require-dev": {
-    "phpunit/phpunit": "^6.2"
+    "phpunit/phpunit": "^6.2",
+    "phpspec/prophecy": "^1.7"
   },
   "authors": [
     {