ci: Update dependency storybook to v8.6.15 [SECURITY] (#1086)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -72,7 +72,7 @@
     "globals": "16.1.0",
     "jsdom": "26.1.0",
     "prettier": "3.5.3",
-    "storybook": "8.6.14",
+    "storybook": "8.6.15",
     "stylelint": "16.19.1",
     "stylelint-config-recess-order": "6.0.0",
     "stylelint-config-standard": "38.0.0",