flake.lock: update zellij

[a-kenji-buildbot]

Automated changes by the update-flake-lock GitHub Action.

Flake lock file updates:

• Updated input 'zellij':
    'github:zellij-org/zellij/1fda2e2c7399f22abed8dd5dd72fe6c367f075d2' (2024-04-30)
  → 'github:zellij-org/zellij/81c5a2a9df7ab47dcbfefa581d8b3b6b92e594bd' (2024-05-02)

Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force