Clean up dependencies

[NoraLoose]

Description

• Add scipy as dependency
• No duplication of packages in ci/environment-regrid.yml
• Remove conda recipe since this is managed elsewhere
• Cleaner conda installation instructions

Related Issues

Checklist

• Tests added/updated for new functionality
• Documentation updated if needed
• Added an entry to docs/releases.md under [Unreleased]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.46%. Comparing base (27a3e1c) to head (ffc25ca).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #27   +/-   ##
=======================================
  Coverage   86.46%   86.46%           
=======================================
  Files          11       11           
  Lines        2157     2157           
=======================================
  Hits         1865     1865           
  Misses        292      292           

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