build(deps): bump slugify from 1.6.8 to 1.6.9 in /backend

Bumps [slugify](https://github.com/simov/slugify) from 1.6.8 to 1.6.9.
- [Changelog](https://github.com/simov/slugify/blob/master/CHANGELOG.md)
- [Commits](https://github.com/simov/slugify/commits)

---
updated-dependencies:
- dependency-name: slugify
  dependency-version: 1.6.9
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

backend/package.json

@@ -86,7 +86,7 @@
     "preview-email": "^3.1.1",
     "pug": "^3.0.4",
     "sanitize-html": "~2.17.2",
-    "slugify": "^1.6.8",
+    "slugify": "^1.6.9",
     "subscriptions-transport-ws": "^0.11.0",
     "trunc-html": "~1.1.2",
     "tslog": "^4.10.2",

backend/yarn.lock

@@ -10142,10 +10142,10 @@ slug@^8.2.2:
   resolved "https://registry.yarnpkg.com/slug/-/slug-8.2.3.tgz#9aa33e532ae9ccddaf55a42abd9bf6a89d5e44d2"
   integrity sha512-fXjhAZszNecz855GUNIwW0+sFPi9WV4bMiEKDOCA4wcq1ts1UnUVNy/F78B0Aat7/W3rA+se//33ILKNMrbeYQ==
 
-slugify@^1.6.8:
-  version "1.6.8"
-  resolved "https://registry.yarnpkg.com/slugify/-/slugify-1.6.8.tgz#0e43855ebc7df24102d04082e0bcc3a344353604"
-  integrity sha512-HVk9X1E0gz3mSpoi60h/saazLKXKaZThMLU3u/aNwoYn8/xQyX2MGxL0ui2eaokkD7tF+Zo+cKTHUbe1mmmGzA==
+slugify@^1.6.9:
+  version "1.6.9"
+  resolved "https://registry.yarnpkg.com/slugify/-/slugify-1.6.9.tgz#610957dea21e56b65e3a153215ef7b265715c8e8"
+  integrity sha512-vZ7rfeehZui7wQs438JXBckYLkIIdfHOXsaVEUMyS5fHo1483l1bMdo0EDSWYclY0yZKFOipDy4KHuKs6ssvdg==
 
 smart-buffer@^4.2.0:
   version "4.2.0"