Remove 'not yet ported warning'

[davidscn]

to be merged at the very end when we merge #160. The website introduction site needs to be adjusted as well.

[uekerman]

The website introduction site needs to be adjusted as well.

Should we do this here? And what exactly do you mean 😁 ?

[davidscn]

We can't, the site is located here https://github.com/precice/precice.github.io/blob/master/pages/tutorials/tutorials.md

[MakisH]

We need to first merge develop and apply the same change for partitioned-pipe and anything else that we may have added since.

[davidscn]

Done. The elastic-tube-1d has still this warning, but there is no valuable README/tutorial at all.