Investigate multiple mappings in trait mapping database

[apriltuesday]

While looking into #427 we found cases of traits being mapped to multiple terms, one more precise than the other. We should confirm whether these are correct and implement processing to ensure these are fixed automatically or curated in future rounds.

Note that currently, existing trait mappings aren't processed if they aren't actively used in ClinVar releases, meaning that obsolete or redundant terms can linger in the mappings file. As part of this we can revisit this decision if needed.