Fix typo in devcontainer.json (#9364)

Merge pull request 9364

.devcontainer/devcontainer.json

@@ -12,15 +12,15 @@
 	// Add the IDs of extensions you want installed when the container is created.
 	"extensions": [
 		"rebornix.Ruby"
-	]
+	],
 	
 	// Use 'forwardPorts' to make a list of ports inside the container available locally.
 	// "forwardPorts": [],
 
 	// Use 'postCreateCommand' to run commands after the container is created.
-	"postCreateCommand": "bundle install",
+	"postCreateCommand": "bundle install"
 
 	// Uncomment to connect as a non-root user. See https://aka.ms/vscode-remote/containers/non-root.
 	// "remoteUser": "vscode"
 
-}
+}