feat(nix): update nixpkgs 64d5d61a405e93b17b2603735d5ea52a3749e78a

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..

• alias.conf
• buflist.conf
• charset.conf
• exec.conf
• fifo.conf
• fset.conf
• logger.conf
• plugins.conf
• relay.conf
• script.conf
• sec.conf
• tcl.conf
• trigger.conf
• weechat.conf
• xfer.conf