Bicep 0.21.1 onwards detects variables with same name but different case, and throws an error

[pjlewisuk]

Bicep has recently upgraded to 0.21.1, and as per the 0.21.1 release notes, a fix was introduce to detect variables with the same name and different cases:
"Catch case-insensitive clashes of type property names (Azure/bicep#11457)"

Codespaces are now coming pre-loaded with Bicep 0.21.1+, and this is causing an error to be thrown when trying to deploy clusters via AKS-C:

/workspaces/AKS-Construction/bicep/network.bicep(173,5) : Error BCP353: The variables "aks_podSubnet", "aks_podsubnet" differ only in casing. The ARM deployments engine is not case sensitive and will not be able to distinguish between them.
/workspaces/AKS-Construction/bicep/network.bicep(192,5) : Error BCP353: The variables "aks_podSubnet", "aks_podsubnet" differ only in casing. The ARM deployments engine is not case sensitive and will not be able to distinguish between them.
/workspaces/AKS-Construction/bicep/network.bicep(409,9) : Warning BCP334: The provided value can have a length as small as 0 and may be too short to assign to a target with a configured minimum length of 3.
/workspaces/AKS-Construction/bicep/main.bicep(130,16) : Error BCP104: The referenced module has errors.

Originally posted by @pjlewisuk in #633 (comment)

[pjlewisuk]

Fixed in #657