deprecated ta4_jetpack

```
2025-04-27 17:17:38: WARNING[Server]: Call to deprecated function 'getpos', use 'get_pos' instead at ...test/.minetest/mods/techage_modpack/ta4_jetpack/init.lua:187
2025-04-27 17:17:38: WARNING[Server]: Call to deprecated function 'get_player_velocity', use 'get_velocity' instead at ...test/.minetest/mods/techage_modpack/ta4_jetpack/init.lua:188
```