chore: Add comment for cache

Author: lqiu96

google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/it/ITBigQueryTest.java

@@ -3510,6 +3510,8 @@ void testQuery() throws InterruptedException {
     String query = "SELECT TimestampField, StringField, BooleanField FROM " + TABLE_ID.getTable();
     QueryJobConfiguration config =
         QueryJobConfiguration.newBuilder(query)
+            // Disable the cache as query plans do not exist from cached results
+            // This will force generation of execution plan
             .setUseQueryCache(false)
             .setDefaultDataset(DatasetId.of(DATASET))
             .build();