Fix atom engine semver in upgrading docs

docs/upgrading/upgrading-your-package.md

@@ -63,7 +63,7 @@ When you are deprecation free and all done converting, upgrade the `engines` fie
 ```json
 {
   "engines": {
-    "atom": ">=0.174.0, <2.0.0"
+    "atom": ">=0.174.0 <2.0.0"
   }
 }
 ```