Removing members not implemented by browsers

[Rumyra]

Checklist — To help your pull request get merged faster, please do following:

1. • Provide a summary of your changes — say what problem you are fixing, what files are changed, what you've done. This doesn't need to be hugely detailed, as we can see exact changes in the "Files changed" tab.

Removing lastModified, delayed and createDelayed(). As we are not adding them to BCD it's also confusing to have them on the landing page

1. • Provide a link to the issue(s) you are fixing, if appropriate, in the form "Fixes ". GitHub will render this in the form "Fixes fix: fixable flaws in Glossary A-D entries #1234", with the issue number linked to the issue. Doing this allows us to figure out what issues you are fixing, as well as helping to automate things (for example the issue will be closed once the PR that fixed it has been merged).

#2514

[Rumyra]

I'm not happy with this conflict - it hasn't highlighted the removed parts - I'm going to use a separate branch for this... pls ignore