Is your feature request related to a problem?

The upstream library for secondary structure analysis, pyDSSP, has fixed a proline-related issue: ShintaroMinami/PyDSSP#2. The MDAnalysis uses its code without DSSP being a dependency, so respective changes should be added to the MDAnalysis codebase.

Describe the solution you'd like

Figure out if the changes add value compared to existing PRO-related workarounds. If yes, find the meaningful code changes, introduce them to MDA codebase, and optionally remove PRO-related workarounds in existing code.

Describe alternatives you've considered

Not doing that seems ok too, I don't expect changes to be big.

Additional context