notmuch: 0.26 -> 0.26.1

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/notmuch/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/05v4k89ni4phwyxvqskr0hji49b5fmck-notmuch-0.26.1/bin/notmuch --help’ got 0 exit code
- ran ‘/nix/store/05v4k89ni4phwyxvqskr0hji49b5fmck-notmuch-0.26.1/bin/notmuch help’ got 0 exit code
- ran ‘/nix/store/05v4k89ni4phwyxvqskr0hji49b5fmck-notmuch-0.26.1/bin/notmuch --version’ and found version 0.26.1
- found 0.26.1 with grep in /nix/store/05v4k89ni4phwyxvqskr0hji49b5fmck-notmuch-0.26.1
- directory tree listing: https://gist.github.com/adeae189f9ac416571a7c0e3beca712f