Upgrade storybook to 8.6.15 (elastic#247310)

## Summary

Upgrade `storybook` from version `8.6.14` to `8.6.15`

(cherry picked from commit b3c1ec5)

# Conflicts:
#	package.json
#	yarn.lock

Author: kc13greiner

package.json

@@ -1633,23 +1633,23 @@
     "@pmmmwh/react-refresh-webpack-plugin": "^0.5.15",
     "@redocly/cli": "^2.12.0",
     "@statoscope/webpack-plugin": "^5.28.2",
-    "@storybook/addon-a11y": "^8.6.3",
-    "@storybook/addon-actions": "^8.6.3",
-    "@storybook/addon-essentials": "^8.6.3",
-    "@storybook/addon-jest": "8.6.3",
-    "@storybook/addon-styling-webpack": "^1.0.1",
-    "@storybook/addon-webpack5-compiler-babel": "^3.0.5",
-    "@storybook/blocks": "^8.6.3",
-    "@storybook/components": "^8.6.3",
-    "@storybook/core-events": "^8.6.3",
-    "@storybook/core-server": "^8.6.3",
-    "@storybook/manager-api": "^8.6.3",
-    "@storybook/preview-api": "^8.6.3",
-    "@storybook/react": "^8.6.3",
-    "@storybook/react-webpack5": "^8.6.3",
-    "@storybook/test": "^8.6.3",
-    "@storybook/theming": "^8.6.3",
-    "@storybook/types": "^8.6.3",
+    "@storybook/addon-a11y": "^8.6.15",
+    "@storybook/addon-actions": "^8.6.15",
+    "@storybook/addon-essentials": "^8.6.15",
+    "@storybook/addon-jest": "8.6.15",
+    "@storybook/addon-styling-webpack": "^2.0.0",
+    "@storybook/addon-webpack5-compiler-babel": "^3.0.6",
+    "@storybook/blocks": "^8.6.15",
+    "@storybook/components": "^8.6.15",
+    "@storybook/core-events": "^8.6.15",
+    "@storybook/core-server": "^8.6.15",
+    "@storybook/manager-api": "^8.6.15",
+    "@storybook/preview-api": "^8.6.15",
+    "@storybook/react": "^8.6.15",
+    "@storybook/react-webpack5": "^8.6.15",
+    "@storybook/test": "^8.6.15",
+    "@storybook/theming": "^8.6.15",
+    "@storybook/types": "^8.6.15",
     "@testing-library/dom": "^10.4.1",
     "@testing-library/jest-dom": "^6.8.0",
     "@testing-library/react": "^16.3.0",
@@ -1925,7 +1925,7 @@
     "sinon": "^19.0.2",
     "sort-package-json": "^3.2.1",
     "source-map": "^0.7.6",
-    "storybook": "^8.6.3",
+    "storybook": "^8.6.15",
     "style-loader": "^4.0.0",
     "stylelint": "^14.16.1",
     "stylelint-scss": "^4.3.0",