fix(yaml): Avoid bool type error

Docs contained an invalid example:

```
ERROR: The Compose file './docker-compose.yml' is invalid because:                                                                                                                   
services.*.restart contains an invalid type, it should be a string 
```

Use quotes to avoid YAML's implicit type conversion.  Someone may also want to do an audit of [other type conversions that might cause problems](https://www.rpatterson.net/blog/docker-gotchas/#yaml-needs-some-zen).

compose/compose-file/compose-file-v2.md

@@ -1538,16 +1538,16 @@ volumes_from:
 `no` is the default restart policy, and it doesn't restart a container under any circumstance. When `always` is specified, the container always restarts. The `on-failure` policy restarts a container if the exit code indicates an on-failure error.
 
 ```yaml
-restart: no
+restart: "no"
 ```
 ```yaml
-restart: always
+restart: "always"
 ```
 ```yaml
-restart: on-failure
+restart: "on-failure"
 ```
 ```yaml
-restart: unless-stopped
+restart: "unless-stopped"
 ```
 
 {: id="cpu-and-other-resources"}