electrum: 3.1.1 -> 3.1.3

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3/bin/.electrum-wrapped -h’ got 0 exit code
- ran ‘/nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3/bin/.electrum-wrapped --help’ got 0 exit code
- ran ‘/nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3/bin/.electrum-wrapped help’ got 0 exit code
- ran ‘/nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3/bin/electrum -h’ got 0 exit code
- ran ‘/nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3/bin/electrum --help’ got 0 exit code
- ran ‘/nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3/bin/electrum help’ got 0 exit code
- found 3.1.3 with grep in /nix/store/lwp0yd15d73bsnq54za1v9df8r8ryl9s-electrum-3.1.3
- directory tree listing: https://gist.github.com/db75e500a00674c62bfac3e757b1721c