flake.lock: Update (#851)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:nix-community/neovim-nightly-overlay/76f571b9189d954b39b75fcf95b77029a59b8372?narHash=sha256-w11FPYngGvHJ%2BF1c%2BSJ/lAa2lsEzSlIiYNd0s6rLxVQ%3D' (2026-03-05)
  → 'github:nix-community/neovim-nightly-overlay/c5ec84c53a477099c10a33d20e3702d2ccf7b856?narHash=sha256-%2BLM56fjXkZqx7IXMq4eWJeDW4d93/UWgrif6c9TOlvo%3D' (2026-03-06)
• Updated input 'neovim-nightly/neovim-src':
    'github:neovim/neovim/843bc1aa8d1596d8665f36b52ab0447f956016b8?narHash=sha256-YGYnYdm2DYbHTb6OZmLExUY/6/ZVC6IUAM3Ydcne8zM%3D' (2026-03-04)
  → 'github:neovim/neovim/7a8d31687940b40ab82081ffe2fac90bbb6e4e19?narHash=sha256-KdHMemEfY5XO1MsmRKlRG95YWTsw3B47eOripGTeazc%3D' (2026-03-05)
• Updated input 'neovim-nightly/nixpkgs':
    'github:NixOS/nixpkgs/400de68cd101e8cfebffea121397683caf7f5a34?narHash=sha256-%2BbllfMsclzbAAPMZTm3K9G/a5lG%2Bs6l18/AyyYLPSIE%3D' (2026-03-04)
  → 'github:NixOS/nixpkgs/66d9241e3dc2296726dc522e62dbfe89c7b449f3?narHash=sha256-/suKbHSaSmuC9UY7G0VRQ3aO%2BQKqxAQPQ19wG7QNkF8%3D' (2026-03-05)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/400de68cd101e8cfebffea121397683caf7f5a34?narHash=sha256-%2BbllfMsclzbAAPMZTm3K9G/a5lG%2Bs6l18/AyyYLPSIE%3D' (2026-03-04)
  → 'github:nixos/nixpkgs/289c8a834fbf87af1f01cb78f479537ef5219a0b?narHash=sha256-thXluFpTTSJDwkJXInd22dx%2Bh9QyjlkcNlbd4bQf0aE%3D' (2026-03-05)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: mrcjkb