Bump rollup from 1.25.2 to 1.26.0 (#29600)

Bumps [rollup](https://github.com/rollup/rollup) from 1.25.2 to 1.26.0.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v1.25.2...v1.26.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -123,7 +123,7 @@
     "npm-run-all": "^4.1.5",
     "popper.js": "^1.16.0",
     "postcss-cli": "^6.1.3",
-    "rollup": "^1.25.2",
+    "rollup": "^1.26.0",
     "rollup-plugin-babel": "^4.3.3",
     "rollup-plugin-commonjs": "^10.1.0",
     "rollup-plugin-istanbul": "^2.0.1",