[Developer Issue]: Remove package installation from setup.qmd

[kellijohnson-NOAA]

Description

• {renv} should take care of all package installation now so we do not need the first two chunks in setup.qmd.
• remove code from setup
• list instructions in README on how to install packages or what packages are needed depending on if renv is used or not

[iantaylor-NOAA]

@Copilot, can you suggest text to add to the README to address the third checkbox in this issue ("list instructions in README on how to install packages or what packages are needed depending on if renv is used or not")? The dependencies are either specified by renv or in the yml files (e.g. https://github.com/NOAA-FIMS/case-studies/blob/main/.github/workflows/render.yml#L61).

Note that other changes to README are subject to this Pull Request: #104