Update testcase link 877 to new test case

What does this MR do?

Updates link from testcase 877 to 1783 as we've reached the comment limit on the old issue. In the future we intend to run a cleanup script to remove all but the last 500 comments on issues to prevent this, but that script hasn't been merged yet #283926 (comment 489334611).

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

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Security

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