Fix typo in api_interfaces.rst

[vavanade]

PR Summary

Fix a typo in docs.

PR Checklist

Linked Issue

• Added "closes #0000" in the PR description to link it to the original issue.

Documentation and Tests

• Has pytest style unit tests (and pytest passes)
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• New plotting related features are documented with examples.

Release Notes

• New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst

[github-actions]

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[ksunden]

Thank you for your contribution, hope to hear from you again!

Rerrunning the doc build CI because it failed,though I don't think it is related to this change, but will hold off on looking too deeply until a second run.