revert hotfix for doubled renewable capacity

[lindnemi]

In myopic optimisation the renewable capacities were added twice. This has recently been noted in #1016, but before that already in #727 and more recently in #1029.

With #1080 the underlying cause has been addressed, and the estimation of renewable capacities in add_electricity has been disabled for myopic foresight (and i think for perfect foresight as well, was this intentional?).

However, before #1080, two hotfixes addressed the problems caused be the doubled renewable capacity, namely #728 and #1022.

This PR removes the hotfixes, which were now causing problems themselves when the grouping_year was equal to the baseyear.

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.