docs: Fix default behavior description for SDL_PROP_APP_METADATA_NAME_STRING.

Fixes #16317.

(cherry picked from commit ddba673cddfa79ce798eca5ba402e0f1a2a2a243)

include/SDL3/SDL_init.h

@@ -426,8 +426,9 @@ extern SDL_DECLSPEC bool SDLCALL SDL_SetAppMetadata(const char *appname, const c
  * - `SDL_PROP_APP_METADATA_NAME_STRING`: The human-readable name of the
  *   application, like "My Game 2: Bad Guy's Revenge!". This will show up
  *   anywhere the OS shows the name of the application separately from window
- *   titles, such as volume control applets, etc. This defaults to "SDL
- *   Application".
+ *   titles, such as volume control applets, etc. If not provided by the app,
+ *   SDL will attempt to pick a reasonable default (the app's binary's name
+ *   if the platform can provide it, or "SDL Application" if all else fails).
  * - `SDL_PROP_APP_METADATA_VERSION_STRING`: The version of the app that is
  *   running; there are no rules on format, so "1.0.3beta2" and "April 22nd,
  *   2024" and a git hash are all valid options. This has no default.