Use conda-forge rdkit-postgresql in README; drop Apple-silicon caveats

[skearnes]

Summary

• rdkit-postgresql is available on Apple silicon via conda-forge (already how CI installs it in tests.yml), so the special-case instructions are no longer needed.
• Switches both READMEs from -c rdkit to -c conda-forge to match CI.

Test plan

• Skim rendered READMEs.

🤖 Generated with Claude Code

Greptile Summary

Both READMEs are updated to replace the -c rdkit channel with -c conda-forge for installing rdkit-postgresql, and the Apple silicon / x86_64-only caveats are dropped. The change is consistent with .github/workflows/tests.yml, which already uses conda install -c conda-forge rdkit-postgresql against both ubuntu-latest and macos-14 runners.

• README.md: Removes the "Apple silicon: use conda install postgresql instead" comment and switches to the conda-forge channel.
• ord_interface/api/README.md: Removes the "rdkit-postgresql is currently only available on x86_64" note and switches to the conda-forge channel.

Confidence Score: 5/5

Documentation-only change; the new instructions exactly match what CI already runs successfully on both Linux and Apple silicon.

Both README files now reflect the conda-forge channel that CI has used all along, and the removed caveats are confirmed obsolete by the macOS CI matrix. No code paths are touched.

No files require special attention.

Important Files Changed

Filename	Overview
README.md	Removes Apple silicon caveat and switches channel from -c rdkit to -c conda-forge, matching CI.
ord_interface/api/README.md	Removes the x86_64-only note and switches channel from -c rdkit to -c conda-forge.

_{Reviews (1): Last reviewed commit: "Merge branch 'main' into readme-rdkit-co..." | Re-trigger Greptile}