CI/dev: fixup compose sidekiq mounts

What does this MR do?

Adds the uploads volume mount to the Sidekiq definition in docker-compose.yml.

There is no functional change to the containers or their operation. This is explicitly for the Docker Compose usage of development and testing.

Details

When attempting to test a deployment of a functional change to gitlab-pages container, it was noticed that we could not create a a project from the Pages/Plain HTML template.

Error:

{
  "component": "gitlab",
  "subcomponent": "exceptions_json",
  "level": "error",
  "severity": "ERROR",
  "time": "2022-12-05T19:29:46.629Z",
  "correlation_id": "01GKHW81ACVY3MKKWV3XHQFS7M",
  "exception.class": "Projects::ImportService::Error",
  "exception.message": "No such file or directory @ rb_file_s_lstat - [FILTERED]",
  ...
}

Finally, the cause was determined to be (via strace) a missing file in /srv/gitlab/uploads/-/system/... because this file is placed by Puma in the Webservice conainer 🤦 Workhorse had this mount shared with Webservice, which is why actually uploading would work, but imports just "have never". So, we add in the appropriate shared Docker volume mount, and viola.

Related issues

gitlab-org/charts/gitlab#2972 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated