test: update test-dns error message
test-dns is in the internet suite and therefore is rarely run. (That will change soon. We will run internet tests nightly in CI.) Because it is infrequently run, it was not noticed that it no longer passes. (An error message has changed to provide more information.) This change fixes the test so it passes.
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
commit message follows commit guidelines