Bug: `SqlImplementation.entities()` doesn't return all members

## Overview
I'm trying to start off some scripting by collecting CURIES of all terms in an ontology. Then, using the keys of a `prefix_map`, I'll filter out all the ones I care about.

In my [omim.db](https://drive.google.com/file/d/1WKq4KqTjcpSHTCdfIxdYq_ZxkJrEGSxl/view?usp=sharing), `ProntoImplementation.entities()` returns a list of ~25,000, while `SqlImplementation.entities()` returns about ~1,500.

Text file w/ all the CURIES: [terms by implementation.txt](https://github.com/INCATools/ontology-access-kit/files/9428891/terms.by.implementation.txt)

Reproduce the discrepancy with the supplied omim.db, comparing the CURIEs returned by SqlImplementation.entities() and ProntoImplementation.entities(). Use the terms by implementation.txt file to inspect which members are missing from the SQL result. Done means SqlImplementation.entities() returns all expected ontology members.

Written by the indexing model from the issue text.