Fix guacrest docker compose healthchecks

[nchelluri]

Description of the PR

In main right now, if you run make container followed by make start-service from the root dir, or GUAC_IMAGE=local-organic-guac docker compose -f guac-demo-compose.yaml up --force-recreate from the container_files dir, and then run docker ps, guacrest will be reported as unhealthy.

This is because the healthcheck uses the wget's --spider flag which makes a HEAD request. But the OpenAPI spec for guacrest does not allow for that method. So I changed the healthcheck command to use the wget's -O- flag instead, which makes a GET request (and doesn't create a file with the response body - which would happen without any -O flag - but instead prints it to standard out).

After my commits, I retested the above docker compose commands and in both cases docker ps shows guacrest as healthy.

fixes #2002

PR Checklist

• All commits have a Developer Certificate of Origin (DCO) -- they are generated using -s flag to git commit.
• All new changes are covered by tests
• If GraphQL schema is changed, make generate has been run
• If GraphQL schema is changed, GraphQL client updates/additions have been made
• If OpenAPI spec is changed, make generate has been run
• If ent schema is changed, make generate has been run
• If collectsub protobuf has been changed, make proto has been run
• All CI checks are passing (tests and formatting)
• All dependent PRs have already been merged

[pxp928]

fixes #2002

[pxp928]

LGTM! Thanks