Add e2e test for disabling source code download

What does this MR do and why?

Related to：https://jihulab.com/gitlab-cn/gitlab/-/issues/4078

Add E2E test for disabling source code download

Testcase：

• https://jihulab.com/gitlab-cn/quality/testcases/-/quality/test_cases/21
• https://jihulab.com/gitlab-cn/quality/testcases/-/quality/test_cases/22

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