Add editor's note about relation b/t OBI & CHEBI: solvent/solvent role

[sebastianduesing]

Closes #1771. Adds an editor's note to OBI:"solvent role" specifying the difference between it and CHEBI:"solvent," using language proposed by @bpeters42.

[bpeters42]

reviewed in OBI call 4/15

[turbomam]

An editor note like this is a good way of adding clarity, but I beleive that, as of April 2024, roles and material entities are disjoint in ChEBI, and this particular editor note is actually misleading.

2024-04-22 OBI call
It is concerning that roles and material entities in ChEBI may have been less clear in the past, and if a change was made, we don't know about it in this OBI call.

[cmungall]

I agree with @turbomam. In fact these branches have always been disjoint.

[bpeters42]

I cannot reconstruct what I had looked at before, and @turbomam and @cmungall are completely right. We should not add this comment, and go back to the issue.

[bpeters42]

Closing this PR to revisit the discussion on the issue itself.