Update composer.json

Author: overtrue

composer.json

@@ -4,7 +4,7 @@
  "require": {
  "php": ">=5.5.9",
  "league/flysystem": "^1.0",
- "overtrue/flysystem-cos": "^1.0.0"
+ "overtrue/flysystem-cos": "^2.0.0"
  },
  "autoload": {
  "psr-4": {