wallust: refactor derivation

1. Remove use of `rec` keyword;
2. Remove parameterization of `pname`;
3. Remove `with lib;` from meta attribute.

pkgs/applications/misc/wallust/default.nix

···
 , rustPlatform
 , nix-update-script
 }:
-rustPlatform.buildRustPackage rec {
+let
+  version = "2.7.1";
+in
+rustPlatform.buildRustPackage {
   pname = "wallust";
-  version = "2.7.1";
+  inherit version;
 
   src = fetchFromGitea {
     domain = "codeberg.org";
     owner = "explosion-mental";
-    repo = pname;
+    repo = "wallust";
     rev = version;
     hash = "sha256-WhL2HWM1onRrCqWJPLnAVMd/f/xfLrK3mU8jFSLFjAM=";
   };
···
 
   passthru.updateScript = nix-update-script { };
 
-  meta = with lib; {
+  meta = {
     description = "A better pywal";
     homepage = "https://codeberg.org/explosion-mental/wallust";
-    license = licenses.mit;
-    maintainers = with maintainers; [ onemoresuza iynaix ];
+    license = lib.licenses.mit;
+    maintainers = with lib.maintainers; [ onemoresuza iynaix ];
     downloadPage = "https://codeberg.org/explosion-mental/wallust/releases/tag/${version}";
-    platforms = platforms.unix;
+    platforms = lib.platforms.unix;
     mainProgram = "wallust";
   };
 }