Ensure trilinos installed before environments section

[becker33]

During the RADIUSS tutorial, @tldahlgren was forced to ad-lib more than usual because an environment with trilinos was taking a long time to install.

Trilinos is also installed during the basics section in two different configurations.

When we next redo these sections, we should ensure that the trilinos that we install in the basics section (and don't uninstall, we uninstall one of them) is the same one used in the environments section.