python39Packages: remove two more aliases

pkgs/top-level/python-aliases.nix

···
   pytestpep8 = throw "pytestpep8 was removed because it is abandoned and no longer compatible with pytest v6.0"; # added 2020-12-10
   pytestquickcheck = pytest-quickcheck; # added 2021-07-20
   pytestrunner = pytest-runner; # added 2021-01-04
+  python-lz4 = lz4; # added 2018-06-01
+  python-pam = pam; # added 2020-09-07.
   pytest_xdist = pytest-xdist; # added 2021-01-04
   python_simple_hipchat = python-simple-hipchat; # added 2021-07-21
   qasm2image = throw "qasm2image is no longer maintained (since November 2018), and is not compatible with the latest pythonPackages.qiskit versions."; # added 2020-12-09

pkgs/top-level/python-packages.nix

···
 
   lyricwikia = callPackage ../development/python-modules/lyricwikia { };
 
-  lz4 = self.python-lz4; # alias 2018-12-05
+  lz4 = callPackage ../development/python-modules/lz4 { };
 
   lzstring = callPackage ../development/python-modules/lzstring { };
 
···
   paho-mqtt = callPackage ../development/python-modules/paho-mqtt { };
 
   palettable = callPackage ../development/python-modules/palettable { };
-
-  # Alias. Added 2020-09-07.
-  pam = self.python-pam;
 
   pamela = callPackage ../development/python-modules/pamela { };
 
···
   python-lsp-server = callPackage ../development/python-modules/python-lsp-server { };
 
   python-ly = callPackage ../development/python-modules/python-ly { };
-
-  python-lz4 = callPackage ../development/python-modules/python-lz4 { };
 
   python-lzf = callPackage ../development/python-modules/python-lzf { };