drop shards_0_15

pkgs/development/tools/build-managers/shards/default.nix

···
 
 in
 rec {
-
-  shards_0_15 = generic {
-    version = "0.15.0";
-    hash = "sha256-/C6whh5RbTBkFWqpn0GqyVe0opbrklm8xPv5MIG99VU=";
-  };
-
   shards_0_17 = generic {
     version = "0.17.0";
     hash = "sha256-f9MptrKalW7gi0J2h0fokkzdjKBVa2TmoPX8BYffqzY=";

pkgs/top-level/all-packages.nix

···
   shallot = callPackage ../tools/misc/shallot { };
 
   inherit (callPackage ../development/tools/build-managers/shards { })
-    shards_0_15
     shards_0_17
     shards;