Bump rollup from 2.19.0 to 2.20.0 (#31251)

Bumps [rollup](https://github.com/rollup/rollup) from 2.19.0 to 2.20.0.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](rollup/rollup@v2.19.0...v2.20.0)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -128,7 +128,7 @@
     "npm-run-all": "^4.1.5",
     "popper.js": "^1.16.1",
     "postcss-cli": "^7.1.1",
-    "rollup": "^2.19.0",
+    "rollup": "^2.20.0",
     "rollup-plugin-istanbul": "^2.0.1",
     "shelljs": "^0.8.4",
     "sirv-cli": "^1.0.3",