update usage strings for consistency

This updates the format of various usage strings to be more consistent
with other parts of the CLI.

- Use `[OPTIONS]` to indicate where command-specific options should be added
- Use `[SERVICE...]` to indicate zero-or-more services
- Remove some usage strings for specific options (e.g. `-e NAME=VAL`), as that
  option is part of the already mentioned `[OPTIONS]` and we don't provide usage
  for each possible option that can be passed.
- Remove `[--]`, which (I think) was needed for the Python implementation, but is
  a general feature to stop processing flag-options.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/reference/docker_compose_kill.yaml

@@ -6,7 +6,7 @@ long: |-
     ```console
     $ docker-compose kill -s SIGINT
     ```
-usage: docker compose kill [options] [SERVICE...]
+usage: docker compose kill [OPTIONS] [SERVICE...]
 pname: docker compose
 plink: docker_compose.yaml
 options: