[v3.11] Payback period fix for SAM-EM

[softwareengineerprogrammer]

Description

Addresses NREL#413 (comment)

Testing & Verification

1. Unit tests added: N/A
2. Unit tests updated: Affected examples regenerated
3. Manual testing: Manually verified only change to regenerated example results is increase in project payback period by 1 year, as expected

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Change Checklist:

Observe the following checklist items if your change includes a new version (see versioning notes and version management docs).

Before merging:

1. Add a CHANGELOG entry: 5dba068

After merging:

1. Push tag(s) to GitHub: git push fork refs/tags/v3.11.1
2. Post a change announcement to the GEOPHIRES Change Announcements Discussion: Will be rolled into Fervo_Project_Cape-5 announcement (Fervo_Project_Cape-5: Multi-Year Construction Timeline and Reservoir Engineering updates #117)

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Sub-PR of #117