fix typo in modify_fates_paramfile.py

[ckoven]

The dimension name for land use in the parameter file didn't match what it was listed as in modify_fates_paramfile.py, so this corrects that.

Description:

n/a

Collaborators:

n/a

Expectation of Answer Changes:

None, python code only.

Checklist

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All checklist items must be checked to enable merging this pull request:

Contributor

• The in-code documentation has been updated with descriptive comments
• The documentation has been assessed to determine if updates are necessary

Integrator

• FATES PASS/FAIL regression tests were run
• Evaluation of test results for answer changes was performed and results provided

Documentation

• Technical Note update:
• User's Guide update:

Test Results:

no testing because only python code.