fix: remove water sourced heat pumps (for now)

[amos-schledorn]

Currently, we assume data for water-sourced heat pumps from the upper uncertainty range in DEA tables, as recommended by DEA for standalone units.
This

• breaks optimistic/pessimistic scenarios
• is likely an overestimate of costs (see e.g. Pieper 2019 who assume all water-sourced heat pumps to be (per MW) cheaper than air-sourced heat pumps)

Changes proposed in this Pull Request

• Remove water-sourced heat pumps (at least for now) to prevent breaking code for optimistic/pessimistic scenarios

Recommendation

From the currently available data, excess-heat sourced heat pumps could deliver good estimates for water-sourced heat pumps. See also DEA tables on seawater-sourced heat pumps.

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Data source for new technologies is clearly stated.
• Newly introduced dependencies are added to environment.yaml (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the GPLv3 license.

[toniseibold]

Thanks - looks good to me - optimistic/pessimistic cost horizon run smoothly now

[cpschau]

Looks good to me too!

[amos-schledorn]

Thanks for the reviews @toniseibold @cpschau!