Fix dev dependency on google/cloud-trace (#91)

Author: chingor13

composer.json

@@ -20,16 +20,10 @@
     "require-dev": {
         "phpunit/phpunit": "4.8.*",
         "squizlabs/php_codesniffer": "2.*",
-        "google/cloud": "dev-trace-v2",
+        "google/cloud-trace": "^0.4",
         "twig/twig": "~2.0",
         "symfony/yaml": "~3.3"
     },
-    "repositories": [
-        {
-            "type": "git",
-            "url": "https://github.com/chingor13/google-cloud-php"
-        }
-    ],
     "conflict": {
         "ext-opencensus": "< 0.1.0"
     },