Adding minor comment

Signed-off-by: Sagar Upadhyaya <sagar.upadhyaya.121@gmail.com>

modules/cache-common/src/test/java/org/opensearch/cache/common/tier/TieredSpilloverCacheTests.java

@@ -152,6 +152,7 @@ public void testComputeIfAbsentWithFactoryBasedCacheCreation() throws Exception
             LoadAwareCacheLoader<String, String> tieredCacheLoader = getLoadAwareCacheLoader();
             tieredSpilloverCache.computeIfAbsent(key, tieredCacheLoader);
         }
+        // Verify on heap cache size.
         assertEquals(onHeapCacheSize, tieredSpilloverCache.getOnHeapCache().count());
         assertEquals(numOfItems1 - onHeapCacheSize, tieredSpilloverCache.getDiskCache().count());
     }