Replace add_zone with create_zone in ha-config-zone.ts

[NoRi2909]

In #22942 we changed ui.panel.config.zone.create_zone to use the correct "Create zone" again.

The ui.panel.config.zone.add_zone string was left untouched and as it turns out this is the one the action button still uses:

This PR fixes this by making the button use the correct and consistent "Create zone" string, too.

Proposed change

Replace reference to ui.panel.config.zone.add_zone with ui.panel.config.zone.create_zone

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

[NoRi2909]

If I checked this correctly, ui.panel.config.zone.add_zone is now orphaned with this change and could also be removed.

[MindFreeze]

If I checked this correctly, ui.panel.config.zone.add_zone is now orphaned with this change and could also be removed.

Yes, please remove ui.panel.config.zone.add_zone

[NoRi2909]

OK, I've added the second commit.

[MindFreeze]

Thanks!