chore: escape Click's wrapping

Escape Click’s Wrapping in `adk deploy agent_engine` example

Merge #4337

### Link to Issue or Description of Change

**2. Or, if no issue exists, describe the change:**

**Problem:**
`adk deploy agent_engine` help message loses newlines in docstring formatting

<img width="749" height="257" alt="スクリーンショット 2026-01-31 13 29 18" src="https://github.com/user-attachments/assets/ede7d9e7-609d-4412-acce-c80e24ec1e2f" />

**Solution:**

Add `\b` on a line by itself before the formatted block

### Testing Plan

This is format improvement of help message, so I think there is no need to add test case.

**Unit Tests:**

- [ ] I have added or updated unit tests for my change.
- [x] All unit tests pass locally.

```
% pytest tests/unittests/cli  # Python 3.13.8
======================= 260 passed, 140 warnings in 7.73s ========================
```

**Manual End-to-End (E2E) Tests:**

Ran `adk deploy agent_engine --help`, then saw

```
  Example:

      # With Express Mode API Key
      adk deploy agent_engine --api_key=[api_key] my_agent

      # With Google Cloud Project and Region
      adk deploy agent_engine --project=[project] --region=[region]
        --display_name=[app_name] my_agent
```

### Checklist

- [x] I have read the [CONTRIBUTING.md](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) document.
- [x] I have performed a self-review of my own code.
- [x] I have commented my code, particularly in hard-to-understand areas.
- [x] I have added tests that prove my fix is effective or that my feature works.
- [x] New and existing unit tests pass locally with my changes.
- [x] I have manually tested my changes end-to-end.
- [x] Any dependent changes have been merged and published in downstream modules.

### Additional context

Same solution as #4258

COPYBARA_INTEGRATE_REVIEW=#4337 from ftnext:escape-wrapping-deploy-agent-engine-example 0944038
PiperOrigin-RevId: 877205878

Author: ftnext

src/google/adk/cli/cli_tools_click.py

@@ -1967,9 +1967,11 @@ def cli_deploy_agent_engine(
 
   Example:
 
+    \b
     # With Express Mode API Key
     adk deploy agent_engine --api_key=[api_key] my_agent
 
+    \b
     # With Google Cloud Project and Region
     adk deploy agent_engine --project=[project] --region=[region]
       --display_name=[app_name] my_agent