update swiftmailer version in Illuminate\Mail

Author: rizqyhi

src/Illuminate/Mail/composer.json

@@ -13,7 +13,7 @@
         "illuminate/log": "4.2.*",
         "illuminate/support": "4.2.*",
         "illuminate/view": "4.2.*",
-        "swiftmailer/swiftmailer": "~5.1"
+        "swiftmailer/swiftmailer": "^6.0"
     },
     "require-dev": {
         "illuminate/queue": "4.2.*"