docs(changelog): add #2127 txpool RPC PendingTxs entry

Author: JayT106

CHANGELOG.md

@@ -14,6 +14,7 @@
 * [#2081](https://github.com/crypto-org-chain/cronos/pull/2081) Upgrade go-ethereum version to `v1.16.9`, enable Osaka hardfork.
 * [#2091](https://github.com/crypto-org-chain/cronos/pull/2091) feat(app): v0.54 upgrade perf optimizations + app-mempool feature.
 * [#2119](https://github.com/crypto-org-chain/cronos/pull/2119) feat(mempool): support direct insert tx via app mempool.
+* [#2127](https://github.com/crypto-org-chain/cronos/pull/2127) feat(mempool): back txpool RPC with app mempool PendingTxs.
 
 ### Bug fixes