Prune CSS about code highlight

[stevenjoezhang]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes was maked (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs in NexT website have been added / updated (for features).

PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

Issue resolved: N/A

What is the new behavior?

• Screenshots with this changes: N/A
• Link to demo site with this changes: N/A

How to use?

In NexT _config.yml:

...

Does this PR introduce a breaking change?

• Yes.
• No.

There is no visual change made by this PR

Test code:

```
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
```

```yaml
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
```

{% codeblock yaml config.yml %}
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
{% endcodeblock %}


```
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
```

```yaml
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
```

{% codeblock yaml config.yml %}
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Natus facilis quae quo architecto incidunt fugiat sapiente, assumenda labore, voluptate consequatur, nam cumque repellat hic vero odit. Quibusdam ipsa dicta at.
{% endcodeblock %}