fix: remove excess args from dockerfile

Description

Optimized Dockerfile for checkup. We don't need to use args and envs defined in Dockerfile, because envs will be set on run.

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Related issue

Examples

docker run sample:

cat <<EOF > project1.yml
- config:
  project: project1
  dbname: postgres
  username: pgai
  epoch: 1
  upload-api-url: http://platform-postgrest.staging.svc.cluster.local
  upload-api-token: 0b87346499cd0c93f790bff8355274ef
EOF

docker run \
-v `pwd`/project1.yml:/project1.yml \
-e CHECKUP_CONFIG_PATH="./project1.yml" \
-e CHECKUP_HOSTS="pgai-staging.staging.svc.cluster.local" \
-e CHECKUP_SNAPSHOT_DISTANCE_SECONDS=10 \
-e PGPASSWORD=password \
registry.gitlab.com/postgres-ai/postgres-checkup:latest \
bash run_checkup.sh