repo: Remove traces of tmux configuration

While I never disliked tmux I have not been using it for absolute ages
now, ever since starting to multiplex with wezterm. Wezterm can (at
least with my current setup) *not* replace all tmux functionality -
especially running multiple sessions in a detachable way on a remote
server - but I have never needed those in a long time now.

Detachable sessions I can create instead with `abduco`.

nvim/.config/nvim/lua/core/mappings.lua

@@ -113,7 +113,7 @@ map("t", "\\\\", [[<C-\><C-n>]], { desc = "exit terminal mode" })
 map("n", "<leader>/", ":noh<cr>", { desc = "remove highlights" })
 
 -- split buffers vertically/horizontally with the leader \ or - (mirrors my
--- tmux setup)
+-- multiplexer setup)
 map("n", "<leader>-", ":sp<cr>", { desc = "open horiz split" })
 map("n", "<leader>\\", ":vsp<cr>", { desc = "open vert split" })
 -- open actual new tab with leader-T