chore(bot): bump sortablejs from 1.15.6 to 1.15.7 in /assets (#656)

Bumps [sortablejs](https://github.com/SortableJS/Sortable) from 1.15.6 to 1.15.7.
- [Release notes](https://github.com/SortableJS/Sortable/releases)
- [Commits](SortableJS/Sortable@1.15.6...1.15.7)

---
updated-dependencies:
- dependency-name: sortablejs
  dependency-version: 1.15.7
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

assets/package-lock.json

@@ -23,7 +23,7 @@
     "phoenix": "^1.8.4",
     "phoenix_live_view": "^1.1.25",
     "prettier": "3.8.1",
-    "sortablejs": "^1.15.6",
+    "sortablejs": "^1.15.7",
     "tailwindcss": "^4.1.11"
   }
 }