Bump @nextcloud/vue from 2.6.1 to 2.6.4

Bumps [@nextcloud/vue](https://github.com/nextcloud/nextcloud-vue) from 2.6.1 to 2.6.4.
- [Release notes](https://github.com/nextcloud/nextcloud-vue/releases)
- [Commits](https://github.com/nextcloud/nextcloud-vue/compare/v2.6.1...v2.6.4

)

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