Should use ContainerRepository instead of ContainerImageName in container builds

[amolenk]

When using azd up to deploy to Azure, the container build emits a warning:

CONTAINER003: The property 'ContainerImageName' was set but is obsolete - please use 'ContainerRepository' instead.

Normally this isn't a problem because it's just a warning, but it'll break the deployment if you specify MSBuildTreatWarningsAsErrors to true (which is useful for maintaining code quality).