rollback jest to v26.0.0

Author: Dou Du

package.json

@@ -71,7 +71,7 @@
     "eslint": "^8.26.0",
     "eslint-config-prettier": "^8.5.0",
     "eslint-plugin-prettier": "^4.2.1",
-    "jest": "^29.2.2",
+    "jest": "^26.0.0",
     "npm-run-all": "^4.1.5",
     "prettier": "^2.7.1",
     "rimraf": "^3.0.2",

src/__tests__/jupyterlab_hide_code.spec.ts

@@ -1,5 +1,5 @@
 /**
- * @jest-environment jsdom
+ * Example of [Jest](https://jestjs.io/docs/getting-started) unit tests
  */
 
 describe('jupyterlab-hide-code', () => {