Fix "Error while reading file" Fish completion

An unbalanced single quote caused Fish to fail to load the completion file with `source: Error while reading file “/etc/fish/completions/docker.fish”`.

Docker-DCO-1.1-Signed-off-by: Andrew France <andrew@avito.co.uk> (github: Odaeus)

contrib/completion/fish/docker.fish

@@ -85,7 +85,7 @@ complete -c docker -A -f -n '__fish_seen_subcommand_from commit' -l run -d 'Conf
 complete -c docker -A -f -n '__fish_seen_subcommand_from commit' -a '(__fish_print_docker_containers all)' -d "Container"
 
 # cp
-complete -c docker -f -n '__fish_docker_no_subcommand' -a cp -d 'Copy files/folders from a container's filesystem to the host path'
+complete -c docker -f -n '__fish_docker_no_subcommand' -a cp -d "Copy files/folders from a container's filesystem to the host path"
 
 # diff
 complete -c docker -f -n '__fish_docker_no_subcommand' -a diff -d "Inspect changes on a container's filesystem"