replace bundle.invocationImage with bundle.installerImage

[VinozzZ]

What does this change

Template variable bundle.invocationImage has been deprecated and replaced with bundle.installerImage

This PR makes this update and make sure that installer image is always referencing to the current running image instead of the original image reference created during build time

What issue does it fix

Closes #1824
[1]: https://getporter.org/src/CONTRIBUTING.md#when-to-open-a-pull-request

Notes for the reviewer

Put any questions or notes for the reviewer here.

Checklist

• Did you write tests?
• Did you write documentation?
• Did you change porter.yaml or a storage document record? Update the corresponding schema file.
• If this is your first pull request, please add your name to the bottom of our Contributors list. Thank you for making Porter better! 🙇‍♀️

Reviewer Checklist

• Comment with /azp run test-porter-release if a magefile or build script was modified
• Comment with /azp run porter-integration if it's a non-trivial PR

[carolynvs]

Everything is great. You just need to update the documentation page to use the new name of the template variable https://getporter.org/authors/templates/#bundle

[carolynvs]

Thank you for the fix! 💖