fix desert region mod: adds missing see_cost #93936

Job	Run time
skip-duplicates-code	5s
skip-duplicates-data	4s
matrix-variables	1s
Basic Build and Test (Clang 10, Ubuntu, Curses)	55m 45s
Clang 14, macOS 12, Tiles, Sound, x64 and arm64 Universal Binary	1h 12m 32s
GCC 9, Curses, LTO	59m 54s
Clang 12, Ubuntu, Tiles, ASan	1h 25m 4s
GCC 11, Ubuntu, Curses, ASan	2h 25m 3s
GCC 12, Ubuntu cross-compile to MinGW-Win64, Tiles, Sound	1h 11m 36s
GCC 9, Ubuntu, Tiles, Sound, CMake	19m 53s
emscripten / Build	2h 28m 25s
	10h 58m 22s

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