General: switch from git-crypt to transcrypt

.gitattributes

@@ -1 +1 @@
-modules/secrets/** filter=git-crypt diff=git-crypt
+modules/secrets/** filter=crypt diff=crypt merge=crypt

modules/system/system.nix

@@ -28,13 +28,16 @@ in
           dconf
           direnv
           git
-          git-crypt # Secrets management
           gnutar
           gzip
           home-manager
           openssh
           sudo
           xz.bin
+          # Packages required for decrypting config files
+          transcrypt
+          openssl
+          xxd
         ];
       };