fix(provisionning_api): Remove parameters that are not set into template

[tcitworld]

Summary

Fixes

• Notice: Undefined index: parameters
• Warning: Invalid argument supplied for foreach()
• Undefined index: targetUrl at /var/www/nc/nextcloud/core/templates/confirmation.php#9

The template is only called by the Provisioning API in apps/provisioning_api/lib/Controller/VerificationController.php, brought in https://github.com/nextcloud/server/pull/28422.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [ ] Tests (unit, integration, api and/or acceptance) are included
• [ ] Screenshots before/after for front-end changes
• [ ] Documentation (manuals or wiki) has been updated or is not required
• [ ] Backports requested where applicable (ex: critical bugfixes)

[tcitworld]

/backport to stable26

[tcitworld]

/backport to stable27

[tcitworld]

/backport to stable28

[nickvergessen]

Since it's pretty clear this thing is not used from any other point, let's move it also into the app, to avoid it being in core/ and therefore seen as "public API"