Restore defaultFormatter

.devcontainer/devcontainer.json

@@ -28,6 +28,7 @@
 				"python.terminal.activateEnvironment": false,
 				"[python]": {
 					"editor.formatOnSave": true,
+					"editor.defaultFormatter": "ms-python.black-formatter",
 					"editor.codeActionsOnSave": {
 						"source.organizeImports": "explicit"
 					}