maltego: apply review comments from maltego init PR

According to what has been discussed in https://github.com/NixOS/nixpkgs/pull/276997#discussion_r1439057992

pkgs/by-name/ma/maltego/package.nix

@@ -20,16 +20,16 @@ stdenv.mkDerivation (finalAttrs: {
   };
 
   postPatch = ''
-      substituteInPlace bin/maltego \
-            --replace /usr/bin/awk ${lib.getExe gawk}
+    substituteInPlace bin/maltego \
+      --replace-fail /usr/bin/awk ${lib.getExe gawk}
   '';
 
-    desktopItems = [
+  desktopItems = [
     (makeDesktopItem {
-      name = finalAttrs.pname;
+      name = "maltego";
       desktopName = "Maltego";
-      exec = finalAttrs.meta.mainProgram;
-      icon = finalAttrs.pname;
+      exec = "maltego";
+      icon = "maltego";
       comment = "An open source intelligence and forensics application";
       categories = [ "Network" "Security" ];
       startupNotify = false;
@@ -62,7 +62,7 @@ stdenv.mkDerivation (finalAttrs: {
 
     cp -aR . "$out/share/maltego/"
 
-    makeWrapper $out/share/maltego/bin/maltego $out/bin/${finalAttrs.meta.mainProgram} \
+    makeWrapper $out/share/maltego/bin/maltego $out/bin/maltego \
       --set JAVA_HOME ${jre} \
       --prefix PATH : ${lib.makeBinPath [ jre ]}
 
@@ -74,7 +74,7 @@ stdenv.mkDerivation (finalAttrs: {
     description = "An open source intelligence and forensics application, enabling to easily gather information about DNS, domains, IP addresses, websites, persons, and so on";
     mainProgram = "maltego";
     maintainers = with maintainers; [ emilytrau d3vil0p3r ];
-    platforms = with platforms; linux ++ darwin;
+    platforms = platforms.unix;
     sourceProvenance = with sourceTypes; [ binaryBytecode ];
     license = licenses.unfree;
   };