Container group cannot be updated

Hello!

I wanted to to use this action for the following use-case:

- Build docker image with GH Actions
- Push docker image to Azure Container Registry with GH Actions
- Deploy the pushed image to Container Instances with GH Actions (this action does it actually)

## Description

For some reason it failed and GH Actions log said that if I wish to update memory, cpu, os, restart strategy (and whatnot) I should delete and create a new ACI.

After some thinking I checked the `actions.yml` and I found these optional inputs with __default values__:

- cpu (default is: 1)
- memory (default is: 1.5)
- restart-policy (default is: Always)

However I created my ACI with 2 cpus, 7GB memory, and OnFailure restart policy.

After I set these _optional_ inputs to actual values in my GitHub Action deployment works.

## Why it is a problem?
I simple want to deploy a new image from the container registry to the container instance. I create my ACI with arm template or Bicep and I don't want to define cpu, memory, os (etc) specific metadata during this action.

## How would be better?
If someone does not defines these inputs, don't set a default value to it. If the action cannot update ACI without them, make these inputs required without default values.

Regards,
roncsak