SCM link missingfor several plugins

[zbynek]

Service(s)

Update center

Summary

Continued from #3181 :

"alibabacloud-credentials", "alibabacloud-ecs", "codebeamer-xunit-uploader", "lambdatest-automation", "r7insight-log-forwarder" "vrealize-automation-8"

for these 6 extensions even SCM url is missing from update-center-actual.json. Since SCM URL can't be obtained from their POMs, update-center2 should use this fallback:
https://github.com/jenkins-infra/update-center2/blob/33273a62564d5259b9dfdfd6f891fe812d32eee4/src/main/java/io/jenkins/update_center/HPI.java#L478 but that somehow fails (?) GitHub API problem?

Reproduction steps

1. Open https://updates.jenkins.io/current/update-center.actual.json in browser
2. type Object.values(JSON.parse(document.body.innerText).plugins).filter(p=>p.title.includes('Alibaba')).map(p=>p.scm)

Expected: array with 2 URLs
Actual: [undefined, undefined]

[zbynek]

minimal failing test:

 @Test
    public void getRepos() {
        System.setProperty("GITHUB_USERNAME", "<username>");
        System.setProperty("GITHUB_PASSWORD", "ghp_<secret>");  /
        assertTrue(GitHubSource.getInstance().isRepoExisting("https://github.com/jenkinsci/alibabacloud-credentials-plugin"));
    }

[zbynek]

OK now, maybe GitHub fixed the issue in their API (?)