notmuch: 0.26 -> 0.26.1

[bfortz]

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

Motivation for this change

While fixing notmuch, minor version bump.
Checked building on staging-18.03 and rebuilding muchsync and neomutt against it.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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