MINOR: Clean up for KafkaAdminClientTest

[tinaselenge]

Remove unnecessary prefix for statically imported function.
Remove unnecessary try/catch for admin calls for tests

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[chia7712]

Remove unnecessary try/catch for admin calls for tests that should fail when exception is thrown.

There are some fail asserts used in lambda function. Maybe we can replace lambda foreach by loop to propagate the exception. Also, the following code can be rewrite by assertThrows(Exception.class, () -> resultData.get(u).get())

                try {
                    resultData.get(u).get();
                    fail("Expected request for user " + u + " to complete exceptionally, but it did not");
                } catch (Exception expected) {
                    // ignore
                }

[chia7712]

LGTM