Automatic merge from submit-queue

Properly nest code blocks

**What this PR does / why we need it**:

Markdown code blocks are adjusted to better display on GitHub. See [rendered](https://github.com/gmile/kubernetes/blob/c3fbec766366d98e434acd44e84f2a4fb4f64a6d/cluster/addons/cluster-loadbalancing/glbc/README.md) version.

**Release note**:

```release-note
Adjust markdown code block in README for Google Load Balancer addon.
```