pantheon.appcenter: 7.3.0 -> 7.4.0 (#257248)

Actually does the bump.

Fixes cb5ce1520a4df91ee5d4e85178c6cbff7171212b.

pkgs/desktops/pantheon/apps/appcenter/default.nix

···
 
 stdenv.mkDerivation rec {
   pname = "appcenter";
-  version = "7.3.0";
+  version = "7.4.0";
 
   src = fetchFromGitHub {
     owner = "elementary";
     repo = pname;
     rev = version;
-    sha256 = "sha256-Lj3j812XaCIN+TFSDAvIgtl49n5jG4fVlAFvrWqngpM=";
+    sha256 = "sha256-L6MGbzzujr4tEB2Cpd7IU+3mOtSCt2hLPw4mOfZ4TkQ=";
   };
 
   nativeBuildInputs = [