build-system/pyproject: Remove python-pip native-input.

gnu/packages/python-science.scm

@@ -2869,7 +2869,6 @@ genetic variation data.")
                          python-hatch-vcs
                          python-hatchling
                          python-numpy
-                         python-pip
                          python-pypa-build
                          python-pytest
                          python-pytest-subprocess

gnu/packages/python-xyz.scm

@@ -30936,7 +30936,6 @@ By default it uses the open Python vulnerability database Safety DB.")
                   texlive-lm
                   texlive-regexpatch
                   texlive-xcolor))
-           python-pip
            python-poetry-core
            python-setuptools))
     (inputs (list pandoc python-pandocfilters))

gnu/packages/shells.scm

@@ -682,7 +682,6 @@ ksh, and tcsh.")
                    (setenv "HOME" "/tmp"))))))
     (native-inputs
      (list git-minimal
-           python-pip
            python-pyte
            python-pytest
            python-pytest-mock