chore: update all ubuntu image families to ubuntu-2204-lts (fixes #512)

[Celestial-0]

This PR updates the deprecated ubuntu-2004-lts image family to ubuntu-2204-lts across the module and example configurations.

• Updated the default value of source_image_family inside the mig-template module.
• Updated all affected example files to reference ubuntu-2204-lts instead of the removed ubuntu-2004-lts image family.

Reason

The ubuntu-2004-lts family has been deprecated and is no longer available in the ubuntu-os-cloud GCP project, causing terraform apply to fail when running multiple examples from this repository.

Testing

• Verified the change by running terraform plan and terraform apply on updated examples inside my GCP environment.
• Verified the image family ubuntu-2204-lts is available via:

gcloud compute images list --project=ubuntu-os-cloud --filter="family=ubuntu-2204-lts"

Related Issue

Fixes #512

Additional Information

This issue was encountered while running examples inside Qwiklabs GCP Cloud Shell.

Note

This issue was encountered while running the Load Balancing: HTTP(S) Load Balancer with Cloud CDN GSP206 lab on Google Cloud Skills Boost. Updating the image family resolves the failure and allows learners to complete the lab successfully.

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[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @Celestial-0!

[apeabody]

Changed to chore as this doesn't include any functional changes to the module itself.

[Celestial-0]

Thank you @apeabody and the team for reviewing and merging this PR! 🙏

I encountered this issue while working through the Google Cloud Skills Boost lab, and I'm glad I could contribute a fix that may help future learners and users. Appreciate the quick review and helpful feedback!

Looking forward to contributing more in the future. 🚀