Removed unused dep

Author: GrahamCampbell

composer.json

@@ -18,8 +18,7 @@
         "php-http/cache-plugin": "^1.6",
         "php-http/client-implementation": "^1.0",
         "php-http/client-common": "^1.9",
-        "php-http/multipart-stream-builder": "^1.0",
-        "symfony/cache": "^3.3|^4.0"
+        "php-http/multipart-stream-builder": "^1.0"
     },
     "require-dev": {
         "graham-campbell/analyzer": "^2.1",