Remove non exact xrefs from Mondo

[matentzn]

• Needs careful @cmungall review.
• Needs to be tested.
• Decide on Remove non-exact xrefs from Mondo for selected sources? #6970

[cmungall]

We used to have a more conservative approach, where we only threw out non-exact for ontologies that we had high quality comprehensive mappings for (e.g. OMIM); we know the end results here will have high recall and precision. For others like ICD10 we would not filter, so we were weighing recall above precision.

Your approach weighs precision more highly, so we'd end up with only ~1k ICD10 mappings, as opposed to ~10k. There is an argument for this but I think it's too big a change for the public release, so I would remove ICD10 SCTID UMLS from your regexp