Update fuel cell values

[danielelerede-oet]

Changes proposed in this Pull Request

This PR updates values for fuel cell from Danish Energy Agency with JRC-EU-TIMES values, mostly due to missing VOM

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.

[euronion]

Not sure about this:

• JRC doesn't provide FOM, we continue to use DEA numbers? -> inconsistent
• JRC VOM is based on H2 costs, but H2 costs are fuel costs for a fuel that is generally produced in ESMs, rather than taken exogeneously

[danielelerede-oet]

@euronion following our discussion I'd rather close this PR!