[rollup-rollback] Rollback rollup upgrade (#2466)

## Summary:

I recently upgraded to Rollup v4 when I did the pnpm upgrade. This caused the
cjs build to fail in `webapp`. I am rolling back to the previous version of
Rollup to fix the build.

The cause of the build failure is that Rollup v4 is not resolving properly
default exports in the `wb-cell` package. This is causing the build to fail
in tests as the CJS build is not able to resolve this properly.

Issue: "none"

## Test plan:

Run the Snapshot release in webapp and verify that tests no longer break.

Author: jandrade

Reviewers: beaesguerra, jandrade

Required Reviewers:

Approved By: beaesguerra

Checks: ✅ Chromatic - Get results on regular PRs (ubuntu-latest, 20.x), ✅ Test / Test (ubuntu-latest, 20.x, 2/2), ✅ Test / Test (ubuntu-latest, 20.x, 1/2), ✅ Lint / Lint (ubuntu-latest, 20.x), ✅ Check build sizes (ubuntu-latest, 20.x), ✅ Publish npm snapshot (ubuntu-latest, 20.x), ✅ Chromatic - Build and test on regular PRs / chromatic (ubuntu-latest, 20.x), ✅ Prime node_modules cache for primary configuration (ubuntu-latest, 20.x), ⏭️  Chromatic - Skip on Release PR (changesets), ✅ Check for .changeset entries for all changed files (ubuntu-latest, 20.x), ✅ gerald, ⏭️  dependabot

Pull Request URL: #2466

.changeset/spicy-donkeys-run.md

@@ -0,0 +1,37 @@
+---
+"@khanacademy/wb-dev-build-settings": patch
+"@khanacademy/wonder-blocks-accordion": patch
+"@khanacademy/wonder-blocks-banner": patch
+"@khanacademy/wonder-blocks-birthday-picker": patch
+"@khanacademy/wonder-blocks-breadcrumbs": patch
+"@khanacademy/wonder-blocks-button": patch
+"@khanacademy/wonder-blocks-cell": patch
+"@khanacademy/wonder-blocks-clickable": patch
+"@khanacademy/wonder-blocks-core": patch
+"@khanacademy/wonder-blocks-data": patch
+"@khanacademy/wonder-blocks-dropdown": patch
+"@khanacademy/wonder-blocks-form": patch
+"@khanacademy/wonder-blocks-grid": patch
+"@khanacademy/wonder-blocks-icon": patch
+"@khanacademy/wonder-blocks-icon-button": patch
+"@khanacademy/wonder-blocks-labeled-field": patch
+"@khanacademy/wonder-blocks-layout": patch
+"@khanacademy/wonder-blocks-link": patch
+"@khanacademy/wonder-blocks-modal": patch
+"@khanacademy/wonder-blocks-pill": patch
+"@khanacademy/wonder-blocks-popover": patch
+"@khanacademy/wonder-blocks-progress-spinner": patch
+"@khanacademy/wonder-blocks-search-field": patch
+"@khanacademy/wonder-blocks-switch": patch
+"@khanacademy/wonder-blocks-testing": patch
+"@khanacademy/wonder-blocks-testing-core": patch
+"@khanacademy/wonder-blocks-theming": patch
+"@khanacademy/wonder-blocks-timing": patch
+"@khanacademy/wonder-blocks-tokens": patch
+"@khanacademy/wonder-blocks-toolbar": patch
+"@khanacademy/wonder-blocks-tooltip": patch
+"@khanacademy/wonder-blocks-typography": patch
+"@khanacademy/wb-codemod": patch
+---
+
+Rollback rollup version from v4 to v2 to prevent an issue with CJS builds in unit tests

package.json

@@ -119,7 +119,7 @@
     "prettier": "^3.4.2",
     "react-refresh": "^0.16.0",
     "remark-gfm": "^4.0.0",
-    "rollup": "^4.32.1",
+    "rollup": "^2.79.2",
     "rollup-plugin-node-externals": "^8.0.0",
     "storybook": "^8.5.2",
     "storybook-addon-pseudo-states": "^4.0.2",