feat(nix): update nixpkgs 64d5d61a405e93b17b2603735d5ea52a3749e78a

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..

• bspwm/
• dunst/
• fish/functions/
• flake8
• ghostty/
• home-manager/
• msmtp/
• nix/
• nvim/ftplugin/
• nvim/lua/kyle/
• offlineimap/
• polybar/
• rofi/
• rofi/themes/
• tmux/