unstructured

44bad216 - rfctr(part): prepare for pluggable auto-partitioners 3 (#3661)

rfctr(part): prepare for pluggable auto-partitioners 3 (#3661) **Summary** Remove unused `include_metadata` parameter. **Additional Context** - The `include_metadata` parameter was originally added circa v0.7.12 as a mechanism for avoiding the "double-decorating" problem on delegating partitioners. - It turns out it doesn't fully address that problem, is now unused, and is unnecessary for the solution we'll be adding as part of pluggable partitioners. - Remove the unnecessary complexity introduced by this unused parameter.