Update install-conda-env.md

[install-conda-env.md](https://github.com/MetOffice/PyPRECIS/blob/main/install-conda-env.md) needs to be updated to reflect changes/additions to various environment yml files

Open install-conda-env.md and compare its instructions with the repository's various environment yml files. Identify the documented setup steps that no longer match or omit recent additions, then update the guide so it reflects those files and verify that the installation instructions are complete.

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