Fix nasa#1542, removed unnecessary call to UT_GetStubEntry() in UT_Co…

[myc-yang]

Checklist (Please check before submitting)

• 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 #1542 by removing unnecessary call to UT_GetStubEntry() in UT_ConfigureGenericStubReturnValue() in ut_assert/src/utstubs.c because the return value will simply be overwritten by the following if-else statement

Testing performed

Expected behavior changes
No impact to behavior

System(s) tested on

• Hardware: PC
• OS: Ubuntu 18.04
• Versions: [e.g. cFE 6.6, OSAL 4.2, PSP 1.3 for mcp750, any related apps or tools]

Additional context
Add any other context about the contribution here.

Third party code
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Contributor Info - All information REQUIRED for consideration of pull request
Michael Yang NASA/GSFC