Fix log message when virtual lock not possible (#28829)

When virtual lock is not possible because JNA is unavailable, we log a
warning message. Yet, this log message refers to mlockall rather than
virtual lock, presumably because of a copy/paste error. This commit
fixes this issue.

server/src/main/java/org/elasticsearch/bootstrap/Natives.java

@@ -70,7 +70,7 @@ final class Natives {
 
     static void tryVirtualLock() {
         if (!JNA_AVAILABLE) {
-            logger.warn("cannot mlockall because JNA is not available");
+            logger.warn("cannot virtual lock because JNA is not available");
             return;
         }
         JNANatives.tryVirtualLock();