Remove redundant test exec libraries

[justsmth]

Description of changes:

• Remove redundant target_link_libraries for test executables.

Call-outs:

• test_support_lib and crypto are already linked to boringssl_gtest_main here:

  aws-lc/crypto/test/CMakeLists.txt

  Line 26 in ebe0892

  target_link_libraries(boringssl_gtest_main boringssl_gtest crypto test_support_lib)

  )

Testing:

With this change, the following warning messages no longer appear:

[497/569] Linking CXX executable crypto/mem_test
ld: warning: ignoring duplicate libraries: 'crypto/libcrypto.a', 'crypto/test/libtest_support_lib.a'
[502/569] Linking CXX executable crypto/mem_set_test
ld: warning: ignoring duplicate libraries: 'crypto/libcrypto.a', 'crypto/test/libtest_support_lib.a'
[517/569] Linking CXX executable crypto/crypto_test
ld: warning: ignoring duplicate libraries: 'crypto/libcrypto.a', 'crypto/test/libtest_support_lib.a'
[548/569] Linking CXX executable ssl/integration_test
ld: warning: ignoring duplicate libraries: 'crypto/libcrypto.a', 'crypto/test/libtest_support_lib.a'
[569/569] Linking CXX executable ssl/ssl_test
ld: warning: ignoring duplicate libraries: 'crypto/libcrypto.a', 'crypto/test/libtest_support_lib.a'

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