remove zsh completion for `docker tag -f`

Signed-off-by: Harald Albers <github@albersweb.de>

contrib/completion/zsh/_docker

@@ -967,7 +967,6 @@ __docker_subcommand() {
         (tag)
             _arguments $(__docker_arguments) \
                 $opts_help \
-                "($help -f --force)"{-f,--force}"[force]"\
                 "($help -):source:__docker_images"\
                 "($help -):destination:__docker_repositories_with_tags" && ret=0
             ;;