Remove the PDF manual

PDF is very 20th century and nobody reads technical documentation this
way anymore.

nixos/doc/manual/default.nix

@@ -122,7 +122,7 @@ let
       <targetset>
         <targetsetinfo>
             Allows for cross-referencing olinks between the manpages
-            and the HTML/PDF manuals.
+            and manual.
         </targetsetinfo>
 
         <document targetdoc="manual">&manualtargets;</document>
@@ -229,29 +229,6 @@ in rec {
     '';
   };
 
-
-  manualPDF = stdenv.mkDerivation {
-    name = "nixos-manual-pdf";
-
-    inherit sources;
-
-    buildInputs = [ libxml2 libxslt dblatex dblatex.tex ];
-
-    buildCommand = ''
-      ${copySources}
-
-      dst=$out/share/doc/nixos
-      mkdir -p $dst
-      xmllint --xinclude manual.xml | dblatex -o $dst/manual.pdf - \
-        -P target.database.document="${olinkDB}/olinkdb.xml" \
-        -P doc.collab.show=0 \
-        -P latex.output.revhistory=0
-
-      mkdir -p $out/nix-support
-      echo "doc-pdf manual $dst/manual.pdf" >> $out/nix-support/hydra-build-products
-    '';
-  };
-
   # Generate the NixOS manpages.
   manpages = stdenv.mkDerivation {
     name = "nixos-manpages";

nixos/release.nix

@@ -96,7 +96,6 @@ in rec {
 
   manual = buildFromConfig ({ pkgs, ... }: { }) (config: config.system.build.manual.manual);
   manualEpub = (buildFromConfig ({ pkgs, ... }: { }) (config: config.system.build.manual.manualEpub));
-  manualPDF = (buildFromConfig ({ pkgs, ... }: { }) (config: config.system.build.manual.manualPDF)).x86_64-linux;
   manpages = buildFromConfig ({ pkgs, ... }: { }) (config: config.system.build.manual.manpages);
   options = (buildFromConfig ({ pkgs, ... }: { }) (config: config.system.build.manual.optionsJSON)).x86_64-linux;