Fixed TextRollingUpgradeIT flaky runs (elastic#134665)

* Fixed TextRollingUpgradeIT flaky runs

* spotless fix

Author: Kubik42

muted-tests.yml

@@ -519,15 +519,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.ccq.MultiClusterSpecIT
   method: test {csv-spec:fork.FiveFork}
   issue: https://github.com/elastic/elasticsearch/issues/134560
-- class: org.elasticsearch.upgrades.TextRollingUpgradeIT
-  method: testIndexing {upgradedNodes=2}
-  issue: https://github.com/elastic/elasticsearch/issues/134600
-- class: org.elasticsearch.upgrades.TextRollingUpgradeIT
-  method: testIndexing {upgradedNodes=3}
-  issue: https://github.com/elastic/elasticsearch/issues/134601
-- class: org.elasticsearch.upgrades.TextRollingUpgradeIT
-  method: testIndexing {upgradedNodes=1}
-  issue: https://github.com/elastic/elasticsearch/issues/134602
 - class: org.elasticsearch.snapshots.SnapshotShutdownIT
   method: testSnapshotShutdownProgressTracker
   issue: https://github.com/elastic/elasticsearch/issues/134620

x-pack/plugin/logsdb/qa/rolling-upgrade/src/javaRestTest/java/org/elasticsearch/upgrades/TextRollingUpgradeIT.java

@@ -81,7 +81,7 @@ public class TextRollingUpgradeIT extends AbstractRollingUpgradeWithSecurityTest
         }""";
 
     // when sorted, this message will appear at the top and hence can be used to validate query results
-    private String smallestMessage;
+    private static String smallestMessage;
 
     public TextRollingUpgradeIT(@Name("upgradedNodes") int upgradedNodes) {
         super(upgradedNodes);