Googletest export

Update example for SetUpTestSuite/TearDownTestSuite to use modern C++ standards.

Currently it is using an outdated C++ construct (defining static member variables separately from the declaration).

PiperOrigin-RevId: 408663014

docs/advanced.md

@@ -926,11 +926,9 @@ class FooTest : public testing::Test {
   void TearDown() override { ... }
 
   // Some expensive resource shared by all tests.
-  static T* shared_resource_;
+  static T* shared_resource_ = nullptr;
 };
 
-T* FooTest::shared_resource_ = nullptr;
-
 TEST_F(FooTest, Test1) {
   ... you can refer to shared_resource_ here ...
 }