az containerapp exec fails with SSL error on public ACA environments

## Problem

`az containerapp exec` fails with an SSL handshake error even on non-VNet (public) ACA environments:

```
ssl.SSLEOFError: [SSL: UNEXPECTED_EOF_WHILE_READING] EOF occurred in violation of protocol (_ssl.c:1032)
```

The same operation works via the Azure Portal Console, suggesting it's a CLI-specific issue.

## Reproduction

1. Deploy a container app to a public ACA environment (no VNet)
2. Run:
```bash
az containerapp exec --name --resource-group --command /bin/bash
```
3. SSL error occurs

## Workaround

Use Azure Portal > Container App > Console > /bin/bash instead.

## Expected behavior

`az containerapp exec` should work on public ACA environments. The SSL websocket connection should succeed when the container is running.

## Environment

- Azure CLI 2.x (latest)
- ACA public environment (no VNet, external ingress)
- Container in Running state
- Windows client