qcal: move sample config to prevent collision

qcard has a sample config file with the same name, if using home-manager
with both qcard and qcal would then lead to a collision

pkgs/tools/networking/qcal/default.nix

···
   # to that config file in the nix store
   preBuild = ''
     substituteInPlace helpers.go \
-      --replace " config-sample.json " " $out/share/config-sample.json "
+      --replace " config-sample.json " " $out/share/qcal/config-sample.json "
   '';
 
   postInstall = ''
-    mkdir -p $out/share
-    cp config-sample.json $out/share/
+    mkdir -p $out/share/qcal
+    cp config-sample.json $out/share/qcal/
   '';
 
   meta = with lib; {