Version gate migration docs link (#84740)
Currently, it always logs 15 migration docs when upgrading, so version
gate it.
```
Results:
0 errors
41 unmodified
0 skipped
0 ok
Time elapsed: 2.276seconds
✔ Codemods have been applied successfully.
Please review the local changes and read the Next.js 15 migration guide to complete the migration.
https://nextjs.org/docs/canary/app/building-your-application/upgrading/version-15
```
