Bump @rollup/plugin-node-resolve in /src/pretix/static/npm_dir

Bumps [@rollup/plugin-node-resolve](https://github.com/rollup/plugins/tree/HEAD/packages/node-resolve) from 13.3.0 to 15.3.0.
- [Changelog](https://github.com/rollup/plugins/blob/master/packages/node-resolve/CHANGELOG.md)
- [Commits](https://github.com/rollup/plugins/commits/node-resolve-v15.3.0/packages/node-resolve)

---
updated-dependencies:
- dependency-name: "@rollup/plugin-node-resolve"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>