fix the man page and zsh completion for `docker images`

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

contrib/completion/zsh/_docker

@@ -1704,7 +1704,7 @@ __docker_subcommand() {
                 "($help -a --all)"{-a,--all}"[Show all images]" \
                 "($help)--digests[Show digests]" \
                 "($help)*"{-f=,--filter=}"[Filter values]:filter:->filter-options" \
-                "($help)--format[Pretty-print containers using a Go template]:template: " \
+                "($help)--format[Pretty-print images using a Go template]:template: " \
                 "($help)--no-trunc[Do not truncate output]" \
                 "($help -q --quiet)"{-q,--quiet}"[Only show numeric IDs]" \
                 "($help -): :__docker_repositories" && ret=0

man/docker-images.1.md

@@ -45,7 +45,7 @@ versions.
    - since=(<image-name>[:tag]|<image-id>|<image@digest>)
 
 **--format**="*TEMPLATE*"
-   Pretty-print containers using a Go template.
+   Pretty-print images using a Go template.
    Valid placeholders:
       .ID - Image ID
       .Repository - Image repository