Replace Minetest mentions with Luanti (#3169)

mods/sfinv/README.txt

@@ -3,10 +3,10 @@ Minetest Game mod: sfinv
 See license.txt for license information.
 
 Simple Fast Inventory.
-A cleaner, simpler, solution to having an advanced inventory in Minetest.
+A cleaner, simpler, solution to having an advanced inventory in Luanti.
 See game_api.txt for this mod's API.
 Available for use outside of MTG here:
-https://forum.minetest.net/viewtopic.php?t=19765
+https://forum.luanti.org/viewtopic.php?t=19765
 
 Authors of source code
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