[Nuxt] Change usage of `nitro.options.srcDir`

[s1gr1d]

nitro.options.srcDir is not available anymore in Nitro v3. The alternative would probably be nitro.options.rootDir

Refernce: nitrojs/nitro#3719

[linear]

JS-1718

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #19343, which was included in the 10.40.0 release.