Fix #1109, Remove unimplemented test stub prototype

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution

• Fixes Stray UT_Stub_SetReturnValue prototype #1109
  • Removes stray (unimplemented) test stub prototype.

Note: unrelated minor typo piggy-backed onto this PR (to to).

Testing performed
GitHub CI actions (incl. Build + Run, Unit Tests etc.) all passing successfully.

Expected behavior changes
No change to behavior (prototype was not implemented).

Contributor Info
Avi Weiss @thnkslprpt