[chronik-client] Fix flaky websocket integration test
Summary: The invalidated/reconsidered block polling depends on timing and results in a flaky test. Moving this case so it happens earlier in the test fixes the issue.
Test Plan:
./contrib/teamcity/build-configurations.py chronik-client-integration-tests
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D16570