Update codecov config to point to master

[lockshaw]

Description of changes:

Related Issues:

Linked Issues:

• Issue #

Issues closed by this PR:

• Closes #

Before merging:

• Did you update the flexflow-third-party repo, if modifying any of the Cmake files, the build configs, or the submodules?

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (master@030bfd6). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1570   +/-   ##
=========================================
  Coverage          ?   78.50%           
=========================================
  Files             ?      867           
  Lines             ?    28904           
  Branches          ?      778           
=========================================
  Hits              ?    22690           
  Misses            ?     6214           
  Partials          ?        0           

Flag	Coverage Δ
unittests	78.50% <ø> (?)

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