[docs] d78b44a further broke `default` cell of `releasedLabels` in `Options` table

It didn't work well before and it got worse after.
https://github.com/semantic-release/github/blame/d78b44ab2d2e1b14ea9368892a278313beaed89e/README.md#L90

before:

after:

The following is closer to what I think is correct, but may need review by someone who can verify the code snippet is correct..

| Option | Description | Default |
| --- | --- | --- |
| `releasedLabels`      | The [labels](https://help.github.com/articles/about-labels) to add to each issue and pull request resolved by the release. Set to `false` to not add any label. See [releasedLabels](#releasedlabels). | ```['released<%= nextRelease.channel ? \` on @\${nextRelease.channel}\` : "" %>']``` |

Although a <pre lang="js"> tag could be used to give Javascript code highlighting, doing so makes the entire Default column very wide. I see why that wasn't done before.

For reference, here's the code block with Javascript highlighting.

['released<%= nextRelease.channel ? \` on @\${nextRelease.channel}\` : "" %>']

Start in README.md around line 90 and inspect the blame for commit d78b44a. Render the options table to compare the releasedLabels default cell with the surrounding documentation and verify the JavaScript example remains readable. Done means the default value is displayed as an intact code span or block without the stray dash or excessive table width.