Googletest export

Add missing InitGoogleTest line in "Registering tests" example code

Copying the original code gives the following error message
"""
IMPORTANT NOTICE - DO NOT IGNORE:
This test program did NOT call testing::InitGoogleTest() before calling RUN_ALL_TESTS(). This is INVALID. Soon Google Test will start to enforce the valid usage. Please fix it ASAP, or IT WILL START TO FAIL.
"""

PiperOrigin-RevId: 408385714

docs/advanced.md

@@ -1597,6 +1597,7 @@ void RegisterMyTests(const std::vector<int>& values) {
 }
 ...
 int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
   std::vector<int> values_to_test = LoadValuesFromConfig();
   RegisterMyTests(values_to_test);
   ...