Closes # (if applicable).

Changes proposed in this Pull Request

Since the Co2 sequestration store is only charged and positive marginal cost of the store in this case reduce the objective function this PR changes the sign of the marginal costs to be negative.

Checklist

• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to envs/environment.yaml.
• Changes in configuration options are added in all of config.default.yaml.
• Changes in configuration options are also documented in doc/configtables/*.csv.
• A release note doc/release_notes.rst is added.