Bump rollup from 2.75.5 to 2.75.7 in /src/pretix/static/npm_dir

Bumps [rollup](https://github.com/rollup/rollup) from 2.75.5 to 2.75.7.
- [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/v2.75.5...v2.75.7)

---
updated-dependencies:
- dependency-name: rollup
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/pretix/static/npm_dir/package.json

@@ -9,7 +9,7 @@
     "@rollup/plugin-babel": "^5.3.1",
     "@rollup/plugin-node-resolve": "^13.3.0",
     "vue": "^2.7.0",
-    "rollup": "^2.75.5",
+    "rollup": "^2.75.7",
     "rollup-plugin-vue": "^5.0.1",
     "vue-template-compiler": "^2.7.0"
   }