Fix invalid format specifier in debug statement.

Closes #4241
Original pull request: #4246

Author: christophstrobl

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/MongoTransactionManager.java

@@ -397,7 +397,7 @@ private static String debugString(@Nullable ClientSession session) {
 				debugString += String.format("causallyConsistent = %s, ", session.isCausallyConsistent());
 				debugString += String.format("txActive = %s, ", session.hasActiveTransaction());
 				debugString += String.format("txNumber = %d, ", session.getServerSession().getTransactionNumber());
-				debugString += String.format("closed = %d, ", session.getServerSession().isClosed());
+				debugString += String.format("closed = %b, ", session.getServerSession().isClosed());
 				debugString += String.format("clusterTime = %s", session.getClusterTime());
 			} else {
 				debugString += "id = n/a";

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/ReactiveMongoTransactionManager.java

@@ -401,7 +401,7 @@ private static String debugString(@Nullable ClientSession session) {
 				debugString += String.format("causallyConsistent = %s, ", session.isCausallyConsistent());
 				debugString += String.format("txActive = %s, ", session.hasActiveTransaction());
 				debugString += String.format("txNumber = %d, ", session.getServerSession().getTransactionNumber());
-				debugString += String.format("closed = %d, ", session.getServerSession().isClosed());
+				debugString += String.format("closed = %b, ", session.getServerSession().isClosed());
 				debugString += String.format("clusterTime = %s", session.getClusterTime());
 			} else {
 				debugString += "id = n/a";