Remove unused hydra input

Author: amesgen

flake.lock

@@ -23,7 +23,6 @@
     "hls-2.7" = { url = "github:haskell/haskell-language-server/2.7.0.0"; flake = false; };
     "hls-2.8" = { url = "github:haskell/haskell-language-server/2.8.0.0"; flake = false; };
     "hls-2.9" = { url = "github:haskell/haskell-language-server/2.9.0.1"; flake = false; };
-    hydra.url = "hydra";
     hackage = {
       url = "github:input-output-hk/hackage.nix";
       flake = false;