chore: bump Jest to v26 (#12190)

.github/workflows/ci.yml

@@ -117,6 +117,10 @@ jobs:
       - name: Install
         run: |
           BABEL_ENV=test-legacy make -j bootstrap-only
+      - name: Downgrade Jest for node <= 8
+        if: matrix.node-version == '6' || matrix.node-version == '8'
+        run: |
+          yarn remove jest && yarn add --dev jest@24
       - uses: actions/download-artifact@v2
         with:
           name: babel-artifact

package.json

@@ -34,7 +34,6 @@
     "@rollup/plugin-json": "^4.1.0",
     "@rollup/plugin-node-resolve": "^9.0.0",
     "@rollup/plugin-replace": "^2.3.3",
-    "babel-jest": "^24.9.0",
     "babel-plugin-transform-charcodes": "^0.2.0",
     "chalk": "^2.4.2",
     "charcodes": "^0.2.0",
@@ -52,7 +51,7 @@
     "gulp-newer": "^1.0.0",
     "gulp-plumber": "^1.2.1",
     "husky": "^3.0.0",
-    "jest": "^24.9.0",
+    "jest": "^26.6.1",
     "lerna-changelog": "^0.5.0",
     "lint-staged": "^9.2.0",
     "mergeiterator": "^1.2.5",