Extension install should not have a default selection prompt

## Describe the bug

**Command Name**
`az containerapp --help` without `containerapp` extension installed prompted me to install software. The software installation prompt had a default value. I accidentally pressed Enter and ended up installing the wrong software.

**Errors:**
No errors.

## To Reproduce:

- Uninstall `containerapp` extension if you already have it installed
- `az containerapp --help`
- The UI prompt comes up for the installation suggestion. The prompt has a default choice selected. I accidentally pressed 'Enter' since it took 4 seconds for the installation suggestion to come up (was trying to type a second command). This ended up installing the wrong software.

## Expected Behavior

An auto-suggested installation prompt should not provide a default choice selected.
1. Selecting the wrong selection ends up installing the wrong software
2. It is an auto-suggested prompt. High chances that it may not be right?

Side note: This did not reproduce consistently, but I expect `az containerapp --help` to be a direct match for `containerapp` and should always be recommended over other fuzzy matches.

## Environment Summary
```
macOS-13.3.1-arm64-arm-64bit, Darwin 22.4.0
Python 3.10.11
Installer: HOMEBREW

azure-cli 2.47.0 *

Extensions:
serviceconnector-passwordless 0.3.1

Dependencies:
msal 1.20.0
azure-mgmt-resource 22.0.0
```
## Additional Context