Use timestampMillis name in CachedAllocationStats record

Author: JeremyDahlgren

server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/TransportGetAllocationStatsAction.java

@@ -208,7 +208,7 @@ public DiskThresholdSettings getDiskThresholdSettings() {
         }
     }
 
-    private record CachedAllocationStats(Map<String, NodeAllocationStats> stats, long timestampMsecs) {}
+    private record CachedAllocationStats(Map<String, NodeAllocationStats> stats, long timestampMillis) {}
 
     private static class AllocationStatsCache {
         private final long maxAgeMillis;
@@ -229,7 +229,7 @@ Map<String, NodeAllocationStats> get() {
 
             final var stats = cachedStats.get();
 
-            if (stats == null || threadPool.relativeTimeInMillis() - stats.timestampMsecs > maxAgeMillis) {
+            if (stats == null || threadPool.relativeTimeInMillis() - stats.timestampMillis > maxAgeMillis) {
                 return null;
             }