Fix old safari but for relative time

[wendevlin]

Proposed change

Older Safari browser (<= iOS 15) havn't been able to show the ha-relative-time because of a browser bug.
A datetime string needs to be "2024-10-21T15:27:00" but we provide it as "2024-10-21 15:27:00". date-fns.parseISO fix this issue for us.

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

Example configuration

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