Fix ErrorProne error which causes nightly to fail

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:testCompile (default-testCompile) on project hbase-server: Compilation failure
[ERROR] /home/jenkins/jenkins-home/workspace/HBase_HBase_Nightly_master/component/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java:[7536,38] error: [ArrayToString] Calling toString on an array does not provide useful information
[ERROR]     (see https://errorprone.info/bugpattern/ArrayToString)
[ERROR]   Did you mean 'fail("the qualifier " + Arrays.toString(q1) + " should be " + v1 + " or " + v2 + ", but " + q1Value);'?
[ERROR] -> [Help 1]