Disable integration test if no expectation file

Disable the "integration test" CI job if there's no gl-sast-report.json or gl-dependency-scanning.json file in the test/expect directory.

Tested manually using the gemnasium-python project:

• integration test job is enabled when there's a JSON report in test/expect, see https://gitlab.com/gitlab-org/security-products/analyzers/gemnasium-python/pipelines/90810488
• integration test job is disabled when there's no JSON report in test/expect, see https://gitlab.com/gitlab-org/security-products/analyzers/gemnasium-python/pipelines/90810811