Update ons-js-toc-container class name to align with other class naming standard

[rmccar]

In the PR #3424 we have updated the table of contents files to remove the toc acronym and move the names of files and classes inline with the other components. There was one class that we could not rename though without creating a breaking change. This was the ons-js-toc-container class, this is because we have documentation that instructs users to set this class on a div to contain the table of contents in some instances (https://service-manual.ons.gov.uk/design-system/components/table-of-contents#example.example-table-of-contents-sticky.nunjucks). Because of this, this is a breaking change and as it doesn't need to be made now we should wait to make it when we are doing our next major release.

[MagdalenaLarge]

Moved to Jira: https://jira.ons.gov.uk/browse/ONSDESYS-203