Update location of hello-greet.h
Fixes
@@ -199,7 +199,7 @@ For example, you could create a test `./test/hello-test.cc`, such as:
```cpp
#include "gtest/gtest.h"
-#include "lib/hello-greet.h"
+#include "main/hello-greet.h"
TEST(HelloTest, GetGreet) {
EXPECT_EQ(get_greet("Bazel"), "Hello Bazel");
