fix: use valid git repository URL format in cookiecutter templates

[v0idheaven]

• I signed and returned the Plone Contributor Agreement, and received and accepted an invitation to join a team in the Plone GitHub organization.
• I verified there aren't any other open pull requests for the same change.
• I followed the guidelines in Contributing to Plone.
• I successfully ran code quality checks on my changes locally.
• I successfully ran tests on my changes locally.
• If needed, I added new tests for my changes.
• If needed, I added documentation for my changes.
• I included a change log entry in my commits.

---

What this does

Fixes the invalid git repository URL format generated in cookiecutter templates.

Changed from SSH format git@github.com:org/repo to valid URI format git+https://github.com/org/repo.git

Applied across all cookiecutter templates in the repo.

Why

The old format fails URI schema validation in tools like Dependency Track.

Closes #263

[davisagli]

__repository_git is used in multiple places and they may not all expect the same format. This needs a more careful analysis.

[v0idheaven]

Hi @davisagli, thank you for the feedback! Could you help me understand which specific places expect a different format? I'll update the fix to only change the files where the git+https:// format is appropriate.

[davisagli]

@v0idheaven I don't have time to do this analysis myself at the moment.