Fix TranslogDeletionPolicy when assertions are disabled (#116654)

Current code causes a NPE when assertions are disabled: the 
openTranslogRef is only non-null when assertions are enabled.

Author: tlrx

server/src/main/java/org/elasticsearch/index/translog/TranslogDeletionPolicy.java

@@ -24,7 +24,7 @@ public final class TranslogDeletionPolicy {
     private final Map<Object, RuntimeException> openTranslogRef;
 
     public void assertNoOpenTranslogRefs() {
-        if (openTranslogRef.isEmpty() == false) {
+        if (Assertions.ENABLED && openTranslogRef.isEmpty() == false) {
             AssertionError e = new AssertionError("not all translog generations have been released");
             openTranslogRef.values().forEach(e::addSuppressed);
             throw e;