Previously, when getting jsdoc for signatures, the services layer would
get the jsdoc tags for the base symbol of a signature if it was
present. This is fine except when the base was overloaded. In that case,
the multiple signatures of the overload would all contribute jsdoc,
which is not correct.

A more correct fix would be to resolve overloads to the base, but
the compiler doesn't have this capability and adding it or jury-rigging
it seems like it would be complex, inappropriate for a fix to ship in a
patch version.

Co-authored-by: Orta Therox <git@orta.io>

Co-authored-by: Orta Therox <git@orta.io>