programs: Use (lib)qalculate(-gtk) from unstable

In 20.09’s version currency conversion is broken.

users/simon/modules/programs.nix

@@ -77,7 +77,7 @@ in
 
     # end user programs
     apacheHttpd # for htpasswd
-    libqalculate # flexible calculator for humans
+    unstable.libqalculate # flexible calculator for humans
     taskwarrior # todo list manager
 
     # passwords
@@ -171,7 +171,7 @@ in
     antimicroX # gamepad to keyboard/mouse mapping
     filezilla # ftp client
     gparted # gui for parted
-    qalculate-gtk # flexible calculator
+    unstable.qalculate-gtk # flexible calculator
     scrcpy # stream/control android phones over adb
     wev # wayland event monitor
     wl-clipboard # not really gui, but cli tool to manage wayland clipboard