gnu: gstreamer: Do not reference Python.

* gnu/packages/gstreamer.scm (gstreamer) [native-inputs]: Replace
python-wrapper with python.
[arguments]: List python in #:disallowed-references.  Add a
'do-not-capture-python phase.

gnu/packages/gstreamer.scm

@@ -475,7 +475,9 @@ the GStreamer multimedia framework.")
          "0aisl8nazcfi4b5j6fz8zwpp0k9csb022zniz65b2pxxpdjayzb0"))))
     (build-system meson-build-system)
     (arguments
-     (list #:phases
+     (list
+      #:disallowed-references (list python)
+      #:phases
       #~(modify-phases %standard-phases
           #$@%common-gstreamer-phases
           #$@(if (string-prefix? "i686" (or (%current-target-system)
@@ -491,7 +493,17 @@ test_stress_cleanup_unschedule.*")
                          (("tcase_add_test \\(tc_chain, \
 test_stress_reschedule.*")
                           "")))))
-                      '()))))
+                 '())
+          (add-after 'patch-shebangs 'do-not-capture-python
+            (lambda _
+              ;; The patch-source-shebangs phase causes the following build
+              ;; script to reference Python in its shebang, which is
+              ;; unnecessary.
+              (substitute* (string-append #$output
+                                          "/libexec/gstreamer-1.0/"
+                                          "gst-plugins-doc-cache-generator")
+                (((which "python3"))
+                 "/usr/bin/env python3")))))))
     (propagated-inputs
      ;; In gstreamer-1.0.pc:
      ;;   Requires: glib-2.0, gobject-2.0
@@ -506,7 +518,7 @@ test_stress_reschedule.*")
            gobject-introspection
            perl
            pkg-config
-           python-wrapper))
+           python))
     (inputs
      (list gmp libcap
            ;; For tests.