SDL_log.h: Remove SDL_MAX_LOG_MESSAGE.

The message length limit was removed in 2.0.24, so there's no need for
this define in SDL3 at all.

Fixes #9467.

docs/README-migration.md

@@ -903,6 +903,9 @@ SDL_LoadFunction() now returns `SDL_FunctionPointer` instead of `void *`, and sh
 
 ## SDL_log.h
 
+The following macros have been removed:
+* SDL_MAX_LOG_MESSAGE - there's no message length limit anymore. If you need an artificial limit, this used to be 4096 in SDL versions before 2.0.24.
+
 The following functions have been renamed:
 * SDL_LogGetOutputFunction() => SDL_GetLogOutputFunction()
 * SDL_LogSetOutputFunction() => SDL_SetLogOutputFunction()

include/SDL3/SDL_log.h

@@ -45,16 +45,6 @@
 extern "C" {
 #endif
 
-
-/**
- * The maximum size of a log message prior to SDL 2.0.24.
- *
- * As of 2.0.24 there is no limit to the length of SDL log messages.
- *
- * \since This macro is available since SDL 3.0.0.
- */
-#define SDL_MAX_LOG_MESSAGE 4096
-
 /**
  * The predefined log categories
  *