[Bug] Cannot update linked backends in ARM/Bicep templates

**Describe the bug**

When a linked backend is already defined, it cannot be changed using a Bicep template.
Simple example:
- I have a linked backend a container app, everything is deployed using Bicep. Works the first time.
- I rename my container app in the Bicep template, I try to redeploy => I get the error One Static Web App can not have more than one linked backend.
- I wait some time, I redeploy again without changing anything: it works again.

**To Reproduce**
Steps to reproduce the behavior:
1. You can use this repo to reproduce the issue: https://github.com/Azure-Samples/nodejs-microservices/tree/main/.azure
2. Fork the repo, and open it in Codespaces
3. Run `az login` in the terminal
4. Run `.azure/infra.sh update` to create the infrastructure
5. Open `.azure/infra/config.json` and replace all occurence of "gateway-api" by "gateway-api-test"
4. Run `.azure/infra.sh update` to update the infrastructure => error

**Expected behavior**
There should not be an error for a use case like this, it's making the deployment not idempotent (sometimes it fails, sometimes not)