remove deprecated grid functions

[FabianHofmann]

The function are deprecated since version v0.2.1

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [ ] I tested my contribution locally and it seems to work fine.
• [ ] I locally ran pytest inside the repository and no unexpected problems came up.
• [ ] I have adjusted the docstrings in the code appropriately.
• [ ] I have documented the effects of my code changes in the documentation doc/.
• [ ] I have added newly introduced dependencies to environment.yaml file.
• [ ] I have added a note to release notes doc/release_notes.rst.
• [ ] I have used pre-commit run --all to lint/format/check my contribution

[codecov[bot]]

Codecov Report

Base: 72.49% // Head: 72.73% // Increases project coverage by +0.23% :tada:

Coverage data is based on head (32af770) compared to base (a2627fe). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #275 +/- ## ========================================== + Coverage 72.49% 72.73% +0.23% ========================================== Files 19 19 Lines 1596 1588 -8 Branches 225 225 ========================================== - Hits 1157 1155 -2 + Misses 369 363 -6 Partials 70 70 ``` | [Impacted Files](https://codecov.io/gh/PyPSA/atlite/pull/275?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=PyPSA) | Coverage Δ | | |---|---|---| | [atlite/cutout.py](https://codecov.io/gh/PyPSA/atlite/pull/275?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=PyPSA#diff-YXRsaXRlL2N1dG91dC5weQ==) | `74.86% <ø> (+2.04%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=PyPSA). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=PyPSA)

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