treewide: use top-level fetchPypi instead of inheriting from the python package set

pkgs/applications/misc/tzupdate/default.nix

···
-{ lib, python3 }:
+{ lib, python3, fetchPypi }:
 
 let
-  inherit (python3.pkgs) buildPythonApplication fetchPypi requests;
+  inherit (python3.pkgs) buildPythonApplication requests;
 in
 buildPythonApplication rec {
   pname = "tzupdate";

pkgs/tools/text/dfmt/default.nix

···
 { lib
 , python3
+, fetchPypi
 }:
 
 let
   inherit (python3.pkgs)
     buildPythonApplication
-    fetchPypi
     pythonOlder;
 in
 buildPythonApplication rec {

pkgs/top-level/all-packages.nix

···
   git-annex-remote-dbx = callPackage ../applications/version-management/git-annex-remote-dbx {
     inherit (python3Packages)
     buildPythonApplication
-    fetchPypi
     dropbox
     annexremote
     humanfriendly;
···
   git-annex-remote-googledrive = callPackage ../applications/version-management/git-annex-remote-googledrive {
     inherit (python3Packages)
     buildPythonApplication
-    fetchPypi
     annexremote
     drivelib
     gitpython

pkgs/top-level/python-packages.nix

···
   maya = callPackage ../development/python-modules/maya { };
 
   mayavi = pkgs.libsForQt5.callPackage ../development/python-modules/mayavi {
-    inherit buildPythonPackage pythonOlder fetchPypi;
+    inherit buildPythonPackage pythonOlder;
     inherit (self) pyface pygments numpy packaging vtk traitsui envisage apptools pyqt5;
   };