Use '=default' to define trivial constructor/destructors

https://clang.llvm.org/extra/clang-tidy/checks/modernize/use-equals-default.html

PiperOrigin-RevId: 526079054
Change-Id: Ia4db21e3e5f58b90de05d52fd94b291ed06d785d

googlemock/test/gmock-actions_test.cc

@@ -985,7 +985,7 @@ TEST(ReturnRoundRobinTest, WorksForVector) {
 
 class MockClass {
  public:
-  MockClass() {}
+  MockClass() = default;
 
   MOCK_METHOD1(IntFunc, int(bool flag));  // NOLINT
   MOCK_METHOD0(Foo, MyNonDefaultConstructible());