Fix #1474, Increase UT_MAX_FUNC_STUBS value

[tandharia]

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
Increases the value of UT_MAX_FUNC_STUBS from 200 to 300 to ensure that a unit test for SCH_ValidateMessageData() in the scheduler app passes successfully

• Fixes Unit test for scheduler app requires increase in UT_MAX_FUNC_STUBS value #1474

Testing performed
Unit testing

Expected behavior changes
Allows the SCH_ValidateMessageData() unit test to run successfully

System(s) tested on
OS: Ubuntu 18.04

Contributor Info - All information REQUIRED for consideration of pull request
Tvisha Andharia - GSFC 582 intern

[skliper]

Why does the SCH test require such a large setting? Has it been confirmed there isn't an issue with the test before upping this value for every test by default?

[tandharia]

The issue has been resolved - the scheduler unit tests have been updated and no longer need this change. I will be closing this pull request and the associated issue