iio-sensor-proxy: 2.2 -> 2.4

Semi-automatic update. These checks were performed:

- built on NixOS
- ran `/nix/store/w1kd60p20ps8v5pjicl3z9s6y4fmkgy0-iio-sensor-proxy-2.4/bin/iio-sensor-proxy -h` got 0 exit code
- ran `/nix/store/w1kd60p20ps8v5pjicl3z9s6y4fmkgy0-iio-sensor-proxy-2.4/bin/iio-sensor-proxy --help` got 0 exit code
- ran `/nix/store/w1kd60p20ps8v5pjicl3z9s6y4fmkgy0-iio-sensor-proxy-2.4/bin/iio-sensor-proxy help` got 0 exit code
- found 2.4 with grep in /nix/store/w1kd60p20ps8v5pjicl3z9s6y4fmkgy0-iio-sensor-proxy-2.4
- found 2.4 in filename of file in /nix/store/w1kd60p20ps8v5pjicl3z9s6y4fmkgy0-iio-sensor-proxy-2.4

cc "@peterhoeg"