DOC: Use correct names of IMPI packages for each installation method

[david-cortes-intel]

Description

I just noticed that the IMPI packages have different names in PyPI and conda:
https://pypi.org/project/impi-rt
https://anaconda.org/channels/conda-forge/packages/impi_rt

This PR updates the documentation to use the correct name according to the installation method.

---

Checklist:

Completeness and readability

• I have updated the documentation to reflect the changes or created a separate PR with updates and provided its number in the description, if necessary.
• Git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details).
• I have resolved any merge conflicts that might occur with the base branch.

Testing

• All CI jobs are green or I have provided justification why they aren't.

[codecov]

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