Docs: fix table on API settings

What does this MR do?

Adds in-page styles to fix the table layout

Before	After

Review app: http://review-docs-docs-yaicna.178.62.207.141.xip.io/ce/api/settings.html#list-of-settings-that-can-be-accessed-via-api-calls

Implemented via https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/331

Related issues

Closes https://gitlab.com/gitlab-com/gitlab-docs/issues/234

Author's checklist

• Apply the correct labels and milestone

Review checklist

• Technical writer's review (required)