docs: update docs for postgresql plugins (#64899)

docs: update docs for postgresql plugins

Co-Authored-By: Mario Rodas <marsam@users.noreply.github.com>

pkgs/servers/sql/postgresql/default.nix

@@ -151,6 +151,9 @@ let
     # below. See #22653
     pathsToLink = ["/" "/bin"];
 
+    # Note: the duplication of executables is about 4MB size.
+    # So a nicer solution was patching postgresql to allow setting the
+    # libdir explicitely.
     postBuild = ''
       mkdir -p $out/bin
       rm $out/bin/{pg_config,postgres,pg_ctl}