delete protein trimerization (GO:0070206) from mop.owl and mop.obo

[StroemPhi]

closes #45

[batchelorc]

only reason for putting it in would be to avoid the code smell of having a single child of trimerisation

[StroemPhi]

@batchelorc I understand the single child problem. But mixing macromolecular and molecular processes is worse, I think.

[StroemPhi]

Any macro-molecular process must be a molecular process off course, so please excuse my lap of thinking. What I actually meant was that inserting this subclass of axiom into GO by asserting it in MOP should be seen as problematic according to OBOFoundry/OBOFoundry.github.io#1443. If I understand that issue thread correctly, we would have to consult with the GO developers first before making such an assertion.