Upgrade gulp-shared-tasks 0.20.0 -> 0.21.0

Author: ehmicky

package-lock.json

@@ -60,7 +60,7 @@
     "execa": "^1.0.0",
     "gulp": "^4.0.0",
     "gulp-execa": "^0.2.0",
-    "gulp-shared-tasks": "^0.20.0",
+    "gulp-shared-tasks": "^0.21.0",
     "has-ansi": "^3.0.0",
     "husky": "^1.3.1",
     "lolex": "^3.1.0",