Adding a note in run_pecan.qmd about installation of PEcAn.SIPNET package

[S1DDHEY]

Summary

fixes #3731
This PR clarifies a missing dependency in the run_pecan.qmd tutorial by documenting the requirement for the PEcAn.SIPNET package

Changes

• Added an inline note in the Write Model Configuration Files section explaining that PEcAn.SIPNET is required for the this demo
• Included the installation command for PEcAn.SIPNET as inline documentation (without adding it as an executable code chunk)

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

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

Checklist:

• My change requires a change to the documentation.
• My name is in the list of CITATION.cff
• I agree that PEcAn Project may distribute my contribution under any or all of
  • the same license as the existing code,
  • and/or the BSD 3-clause license.
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.