[BUILD] Remove gmock from GTEST_BOTH_LIBRARIES

[ThomsonTan]

Based on this CMake doc, GTEST_BOTH_LIBRARIES should just be gtest and gtest_main. gmock should be not included.

I found that there is linking ambiguity if both gtest and gmock are linked to a test dynamically, like the gtest UnitTest are registered to the static registries in gmock DLL, and make the tests not discoverable later by gtest.

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2437 (cb93e9c) into main (4bd64c9) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2437   +/-   ##
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  Coverage   87.06%   87.06%           
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  Files         199      199           
  Lines        6087     6087           
=======================================
  Hits         5299     5299           
  Misses        788      788