Fix GetDirectoryFiles description

The comment sais it allows max 256 files, but the MAX_DIRECTORY_FILES
define actually is set to 512.

src/core.c

@@ -1629,7 +1629,7 @@ const char *GetWorkingDirectory(void)
     return currentDir;
 }
 
-// Get filenames in a directory path (max 256 files)
+// Get filenames in a directory path (max 512 files)
 // NOTE: Files count is returned by parameters pointer
 char **GetDirectoryFiles(const char *dirPath, int *fileCount)
 {