newt: 0.52.15 -> 0.52.20

Semi-automatic update. These checks were performed:

- built on NixOS
- ran `/nix/store/xbjik2b7dbm76gjy47mrvi27iwri304z-newt-0.52.20/bin/whiptail -h` got 0 exit code
- ran `/nix/store/xbjik2b7dbm76gjy47mrvi27iwri304z-newt-0.52.20/bin/whiptail --help` got 0 exit code
- ran `/nix/store/xbjik2b7dbm76gjy47mrvi27iwri304z-newt-0.52.20/bin/whiptail -v` and found version 0.52.20
- ran `/nix/store/xbjik2b7dbm76gjy47mrvi27iwri304z-newt-0.52.20/bin/whiptail --version` and found version 0.52.20
- found 0.52.20 with grep in /nix/store/xbjik2b7dbm76gjy47mrvi27iwri304z-newt-0.52.20
- found 0.52.20 in filename of file in /nix/store/xbjik2b7dbm76gjy47mrvi27iwri304z-newt-0.52.20

cc "@viric"