Fix powerplantmatching problem for DRC

[davide-f]

Closes #349

Changes proposed in this Pull Request

This fix aims at addressing the issue discussed in #349.
The country name standard in pycountry sometimes is conflicting to the value used in other datasets, such as GEO and GPD.
In the specific case of 349, DRC is named "Congo, The Democratic Republic of" (pycountry), while in GEO and GPD is "Democratic Republic of Congo".
That lead to conflicts that are now fixed, yet to be verified at Africa and Earth scale.
It is worth mentioning on pycountry as well.

Checklist

• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Newly introduced dependencies are added to envs/environment.yaml and envs/environment.docs.yaml.
• Changes in configuration options are added in all of config.default.yaml, config.tutorial.yaml, and test/config.test1.yaml.
• Changes in configuration options are also documented in doc/configtables/*.csv and line references are adjusted in doc/configuration.rst and doc/tutorial.rst.
• A note for the release notes doc/release_notes.rst is amended in the format of previous release notes, including reference to the requested PR.

[pz-max]

Quite a special fix 👍 Needs probably revision at later stage.
Let's merge and wait until the next problem arise