fix(deps): update dependency @vercel/og to v0.6.8

Author: renovate[bot]

package.json

@@ -18,7 +18,7 @@
     "@primer/octicons-react": "19.15.1",
     "@tailwindcss/forms": "0.5.10",
     "@tanstack/react-query": "^4.29.12",
-    "@vercel/og": "0.6.5",
+    "@vercel/og": "0.6.8",
     "dayjs": "1.11.13",
     "next": "15.2.4",
     "next-pwa": "5.6.0",