build(deps): update handlebars requirement

Updates the requirements on [handlebars](https://github.com/handlebars-lang/handlebars.js) to permit the latest version.
- [Release notes](https://github.com/handlebars-lang/handlebars.js/releases)
- [Changelog](https://github.com/handlebars-lang/handlebars.js/blob/v4.7.8/release-notes.md)
- [Commits](handlebars-lang/handlebars.js@v4.7.7...v4.7.8)

---
updated-dependencies:
- dependency-name: handlebars
  dependency-type: direct:production
...

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

superset-frontend/plugins/plugin-chart-handlebars/package.json

@@ -27,7 +27,7 @@
     "access": "public"
   },
   "dependencies": {
-    "handlebars": "^4.7.7",
+    "handlebars": "^4.7.8",
     "just-handlebars-helpers": "^1.0.19"
   },
   "peerDependencies": {