[nostalgia/core] Change TileSheet version conv pixels copy to a move

src/nostalgia/core/typeconv.cpp

@@ -41,7 +41,7 @@ struct TileSheetV1ToV2Converter: public Converter {
 		v2->subsheet.size    = v1.pixels.size();
 		v2->defaultPalette   = v1.defaultPalette;
 		v2->pal              = v1.pal;
-		v2->pixels           = v1.pixels;
+		v2->pixels           = std::move(v1.pixels);
 		return OxError(0);
 	}
 };