Tune down generation of null values in LogsDB data generation (#112890) (#112951)

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

test/framework/src/main/java/org/elasticsearch/logsdb/datageneration/datasource/DefaultWrappersHandler.java

@@ -27,7 +27,8 @@ public class DefaultWrappersHandler implements DataSourceHandler {
     }
 
     private static Function<Supplier<Object>, Supplier<Object>> injectNulls() {
-        return (values) -> () -> ESTestCase.randomBoolean() ? null : values.get();
+        // Inject some nulls but majority of data should be non-null (as it likely is in reality).
+        return (values) -> () -> ESTestCase.randomDouble() <= 0.05 ? null : values.get();
     }
 
     private static Function<Supplier<Object>, Supplier<Object>> wrapInArray() {