update comments

contracts/test/TestAggregatorV3.sol

@@ -87,7 +87,7 @@ contract TestAggregatorV3 is AggregatorV3Interface {
         );
     }
 
-    // for debug only
+    // won't use in production, just for knowing how roundId works
     // https://docs.chain.link/docs/historical-price-data/#roundid-in-proxy
     function computeRoundId(uint16 phaseId, uint64 aggregatorRoundId) external pure returns (uint80) {
         return uint80((uint256(phaseId) << 64) | aggregatorRoundId);