build: bump @netlify/plugin-nextjs

Fixes "Outdated plugins" warning in Netlify build logs

Author: wackerow

package.json

@@ -106,7 +106,7 @@
   "devDependencies": {
     "@chromatic-com/playwright": "^0.12.4",
     "@chromatic-com/storybook": "1.5.0",
-    "@netlify/plugin-nextjs": "^5.10.0",
+    "@netlify/plugin-nextjs": "^5.12.0",
     "@playwright/test": "^1.52.0",
     "@storybook/addon-essentials": "8.6.14",
     "@storybook/addon-interactions": "8.6.14",