lib: remove mapAttrsFlatten after a year (#450420)

doc/release-notes/rl-2511.section.md

@@ -301,6 +301,8 @@
 - `reaction` has been updated to version 2, which includes some breaking changes.
   For more information, [check the release article](https://blog.ppom.me/en-reaction-v2).
 
+- `lib.mapAttrsFlatten` has been removed, following its deprecation in NixOS 24.11. Use `lib.attrsets.mapAttrsToList` instead.
+
 - `lib.options.mkPackageOptionMD` has been removed, following its deprecation in NixOS 24.11. Use `lib.options.mkPackageOption` instead.
 
 - The `buildPythonPackage` and `buildPythonApplication` functions now require

lib/default.nix

@@ -552,7 +552,6 @@ let
         modifySumArgs
         innerClosePropagation
         closePropagation
-        mapAttrsFlatten
         nvs
         setAttr
         setAttrMerge

lib/deprecated/misc.nix

@@ -29,11 +29,8 @@ let
     nameValuePair
     tail
     toList
-    warn
     ;
 
-  inherit (lib.attrsets) removeAttrs mapAttrsToList;
-
   # returns default if env var is not set
   maybeEnv =
     name: default:
@@ -278,9 +275,6 @@ let
 
   closePropagation = if builtins ? genericClosure then closePropagationFast else closePropagationSlow;
 
-  # calls a function (f attr value ) for each record item. returns a list
-  mapAttrsFlatten = warn "lib.misc.mapAttrsFlatten is deprecated, please use lib.attrsets.mapAttrsToList instead." mapAttrsToList;
-
   # attribute set containing one attribute
   nvs = name: value: listToAttrs [ (nameValuePair name value) ];
   # adds / replaces an attribute of an attribute set
@@ -470,7 +464,6 @@ in
     innerClosePropagation
     innerModifySumArgs
     lazyGenericClosure
-    mapAttrsFlatten
     maybeAttr
     maybeAttrNullable
     maybeEnv