Revert "deps: update dependency org.assertj:assertj-core to v3 (#1786)" (#2081)
Revert "deps: update dependency org.assertj:assertj-core to v3 (#1786)" (#2081)

This reverts commit 69fcabf478c6fab23c4da3fcc516f820cc178a5b.
googleapis/java-bigquery,googleapis/java-bigquery,googleapis/java-bigquery