fix: can't delete GitHub Enterprise servers

[carlossg]

Description

can't delete GitHub Enterprise servers in Jenkins configuration

Submitter checklist

• Link to JIRA ticket in description, if appropriate.
• Change is code complete and matches issue description
• Automated tests have been added to exercise the changes
• Reviewer's manual test instructions provided in PR description. See Reviewer's first task below.

Reviewer checklist

• Run the changes and verify that the change matches the issue description
• Reviewed the code
• Verified that the appropriate tests have been written or valid explanation given

Documentation changes

• Link to jenkins.io PR, or an explanation for why no doc changes are needed

Users/aliases to notify

[bitwiseman]

@carlossg Ping? Do you plan to finish this?

[carlossg]

flaky tests on Java 8 ?

[jtnord]

flaky tests on Java 8 ?

nope - deterministic spotbugs issue. https://ci.jenkins.io/job/Plugins/job/github-branch-source-plugin/job/PR-400/39/spotbugs/source.53d2e029-62c1-4810-9467-52517f349249/#62

[carlossg]

that explains a lot