Updated default version of Kubernetes to 1.26.6

[pjlewisuk]

... following deprecation of 1.24 on AKS

PR Summary

Updated all references to "1.25.6" to "1.26.3":

• bicep/main.bicep
• helper/src/config.json
• samples/SampleAppMain.json
• samples/SystemPresetExample.json
• samples/shared-acr/main.json

Fixes #626

PR Checklist

• PR has a meaningful title
• Summarized changes
• This PR is ready to merge and is not Work in Progress
• Link to a filed issue
• Screenshot of UI changes (if PR includes UI changes)

[khowling]

Hey, thanks for the update! We do tend to follow the default kubernetes version from the portal, so when aks pg are happy to bump the version, we follow. Today looks like that is 1.25.11

[pjlewisuk]

Hi Keith,

It looks like different regions have different default versions, for example East US and UK South both have 1.26.6 as their default:

Whereas West Europe and Central US still have 1.25.11 as their default:

This seems to correlate with the release they're running: regions on Release v20230730 or newer are defaulting to 1.26.6, whereas regions still on Release v20230723 are defaulting to 1.25.11.

If you like, we can wait until all regions are on release v20230830 or higher on the Release tracker?

[khowling]

Thanks for that Paul, approving!