pidgin-xmpp-receipts: 0.7 -> 0.8

Semi-automatic update. These checks were performed:

- built on NixOS
- found 0.8 with grep in /nix/store/di49z3ic9sk7mrg6rhf0c67qk8pda3kg-pidgin-xmpp-receipts-0.8
- found 0.8 in filename of file in /nix/store/di49z3ic9sk7mrg6rhf0c67qk8pda3kg-pidgin-xmpp-receipts-0.8

cc "@orivej"