SDL_main.h: Minor documentation tweaks.

include/SDL3/SDL_main.h

@@ -156,11 +156,11 @@
 /**
  * Inform SDL to use the main callbacks instead of main.
  *
- * SDL does not define this macro, but will check if it is defined to any
- * value in SDL_main.h. If defined, SDL will expect the app to provide several
- * functions: SDL_AppInit, SDL_AppEvent, SDL_AppIterate, and SDL_AppQuit. The
- * app should not provide a `main` function in this case, and doing so will
- * likely cause the build to fail.
+ * SDL does not define this macro, but will check if it is defined when
+ * including `SDL_main.h`. If defined, SDL will expect the app to provide
+ * several functions: SDL_AppInit, SDL_AppEvent, SDL_AppIterate, and
+ * SDL_AppQuit. The app should not provide a `main` function in this case, and
+ * doing so will likely cause the build to fail.
  *
  * Please see [README/main-functions](README/main-functions), (or
  * docs/README-main-functions.md in the source tree) for a more detailed