Update Ruby dependencies (#189)
Update Ruby dependencies (#189)

This fixes a security vulnerability reported by GitHub's
automatic detection tool.
minetest/minetest.github.io,minetest/minetest.github.io,rubenwardy/minetest.github.io,luk3yx/minetest.github.io,luk3yx/minetest.github.io,rubenwardy/minetest.github.io,minetest/minetest.github.io,rubenwardy/minetest.github.io,luk3yx/minetest.github.io