libpng_apng: drop

It's been the same as libpng since 8164d28, because
`libpng_apng = libpng.override { apngSupport = true; };`, but `apngSupport ? true`

pkgs/applications/science/math/cemu/default.nix

@@ -7,7 +7,7 @@
 , qtbase
 , qmake
 , git
-, libpng_apng
+, libpng
 , pkg-config
 , wrapQtAppsHook
 , stdenv
@@ -37,7 +37,7 @@ stdenv.mkDerivation rec {
     libarchive
     libusb-compat-0_1
     qtbase
-    libpng_apng
+    libpng
   ];
 
   qmakeFlags = [

pkgs/top-level/aliases.nix

@@ -601,6 +601,7 @@ mapAliases ({
   liblrdf = throw "'liblrdf' has been renamed to/replaced by 'lrdf'"; # Converted to throw 2022-02-22
   libmsgpack = throw "'libmsgpack' has been renamed to/replaced by 'msgpack'"; # Converted to throw 2022-02-22
   libosmpbf = throw "libosmpbf was removed because it is no longer required by osrm-backend";
+  libpng_apng = throw "libpng_apng has been removed, because it is equivalent to libpng"; # Added 2021-03-21
   libqmatrixclient = throw "libqmatrixclient was renamed to libquotient"; # Added 2020-04-09
   libqrencode = throw "'libqrencode' has been renamed to/replaced by 'qrencode'"; # Converted to throw 2022-02-22
   librdf = lrdf; # Added 2020-03-22

pkgs/top-level/all-packages.nix

@@ -18690,7 +18690,6 @@ with pkgs;
   libplacebo = callPackage ../development/libraries/libplacebo { };
 
   libpng = callPackage ../development/libraries/libpng { };
-  libpng_apng = libpng.override { apngSupport = true; };
   libpng12 = callPackage ../development/libraries/libpng/12.nix { };
 
   libpostal = callPackage ../development/libraries/libpostal { };
@@ -25954,7 +25953,6 @@ with pkgs;
   firefoxPackages = recurseIntoAttrs (callPackage ../applications/networking/browsers/firefox/packages.nix {
     callPackage = newScope {
       inherit (rustPackages) cargo rustc;
-      libpng = libpng_apng;
       gnused = gnused_422;
       inherit (darwin.apple_sdk.frameworks) CoreMedia ExceptionHandling
                                             Kerberos AVFoundation MediaToolbox
@@ -29440,7 +29438,6 @@ with pkgs;
   thunderbirdPackages = recurseIntoAttrs (callPackage ../applications/networking/mailreaders/thunderbird/packages.nix {
     callPackage = newScope {
       inherit (rustPackages) cargo rustc;
-      libpng = libpng_apng;
       gnused = gnused_422;
       inherit (darwin.apple_sdk.frameworks) CoreMedia ExceptionHandling
                                             Kerberos AVFoundation MediaToolbox