Do not print skipped test's messages in brief mode

[hsaunders1904]

Prevents messages from skipped tests being displayed when the --gtest_brief flag is set.

Resolves #4548

Using this example:

// test.cpp
#include <gtest/gtest.h>

TEST(Test, TwoAndTwoIsFour) { 
  GTEST_SKIP();
  EXPECT_EQ(2 + 2, 4); 
}

TEST(Test, FiveAndFiveIsTen) {
  GTEST_SKIP() << "user message";
  EXPECT_EQ(5 + 5, 10);
}

Before:

$ ./test --gtest_brief=1
.../test.cpp:5: Skipped


.../test.cpp:10: Skipped
user message

[==========] 2 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 0 tests.
[  SKIPPED ] 2 tests.

After:

$ ./test --gtest_brief=1
[==========] 2 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 0 tests.
[  SKIPPED ] 2 tests.

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[Roman-]

This is a perfect MR with minimal code changes that fixes an annoying GTest issue. @google please just merge it.