[BUG] Latest gmx grommp raises exception if tau-p isn't at least 25x dt

[lohedges]

For c-rescale, the latest version of gmx grompp will error if the tau-p parameter isn't at least 25x the value of dt. Our default config should be updated accordingly.

[lohedges]

This is another instance of something that has been adjusted in the sandpit, but never propagated back.