python: Remove pip completion from prezto local

pip completion is bundled with Zsh 5.9. Remove it from prezto local to
avoid shadowing the bundled completion.

modules/python/functions/_pip

@@ -1,19 +0,0 @@
-#compdef -P pip[0-9.]#
-#autoload
-
-#
-# Pip completion, delegating to pip to do all the completion work.
-#
-# Authors:
-#   Indrajit Raychaudhuri <irc@indrajit.com>
-#
-
-if (( $+commands[$words[1]] )); then
-
-  function _pip_completion {
-    compadd -- $( COMP_WORDS="$words[*]" COMP_CWORD=$(( CURRENT - 1 )) \
-                  PIP_AUTO_COMPLETE=1 $words[1] 2>/dev/null )
-  }
-  _pip_completion "$@"
-
-fi