Bump unified_inventory from `3fffa41` to `b1c85a2`

Bumps [unified_inventory](https://github.com/minetest-mods/unified_inventory) from `3fffa41` to `b1c85a2`.
- [Release notes](https://github.com/minetest-mods/unified_inventory/releases)
- [Commits](https://github.com/minetest-mods/unified_inventory/compare/3fffa41eaf68ba749f276310f77da629821613f5...b1c85a2cb808c4effc1a52b519b65d73e4f25fb2)

unified_inventory @ b1c85a2c

-Subproject commit 3fffa41eaf68ba749f276310f77da629821613f5
+Subproject commit b1c85a2cb808c4effc1a52b519b65d73e4f25fb2