Switch to Agent 6+ signature in check integration test

[florimondmanca]

What does this PR do?

The check template was generating a test using the legacy MyCheck(name, init_config, agentConfig) signature (A5). Or maybe this was a typo. In any case, this PR updates the test template to use the proper A6/A7 signature.

Motivation

Encourage usage of up-to-date signature for new integrations.

Additional Notes

Discovered while working on #5715. Refs #5573.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[codecov]

Codecov Report

Merging #5718 into master will decrease coverage by 3.82%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
datadog_checks_dev/tests/common.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/conftest.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/test__env.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/test_utils.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/test_docker.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/test_conditions.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/test_structures.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/test_subprocess.py	100.00% <0.00%> (ø)	⬆️
datadog_checks_dev/datadog_checks/dev/env.py	43.18% <0.00%> (ø)	⬆️
datadog_checks_dev/tests/tooling/test_dep.py	95.09% <0.00%> (ø)	⬆️
... and 886 more