ci/eval/compare: ping maintainers of removed packages

This change pings maintainers of actually removed packages, aka where
the package's expression is deleted.

This will not ping maintainers of packages that become invisible,
because a (transitive) dependency of them is marked as insecure or
broken.

(cherry picked from commit 540e188796)

ci/eval/compare/default.nix

@@ -78,6 +78,7 @@ let
   diffAttrs = builtins.fromJSON (builtins.readFile "${combinedDir}/combined-diff.json");
 
   rebuildsPackagePlatformAttrs = convertToPackagePlatformAttrs diffAttrs.rebuilds;
+  removedPackagePlatformAttrs = convertToPackagePlatformAttrs diffAttrs.removed;
 
   changed-paths =
     let
@@ -117,6 +118,7 @@ let
   maintainers = callPackage ./maintainers.nix { } {
     changedattrs = lib.attrNames (lib.groupBy (a: a.name) rebuildsPackagePlatformAttrs);
     changedpathsjson = touchedFilesJson;
+    removedattrs = lib.attrNames (lib.groupBy (a: a.name) removedPackagePlatformAttrs);
     inherit byName;
   };
 in

ci/eval/compare/maintainers.nix

@@ -5,6 +5,7 @@
 {
   changedattrs,
   changedpathsjson,
+  removedattrs,
   byName ? false,
 }:
 let
@@ -24,7 +25,7 @@ let
   enrichedAttrs = builtins.map (name: {
     path = lib.splitString "." name;
     name = name;
-  }) changedattrs;
+  }) (changedattrs ++ removedattrs);
 
   validPackageAttributes = builtins.filter (
     pkg: