fix: cat returning erros for app rejection (backport #2340) (#2351)

Fixes #2341

<hr>This is an automatic backport of pull request #2340 done by
[Mergify](https://mergify.com).

---------

Co-authored-by: nina / ნინა <[email protected]>
Co-authored-by: Callum Waters <[email protected]>

Author: 3 people

mempool/cat/pool.go

@@ -332,7 +332,7 @@ func (txmp *TxPool) TryAddNewTx(tx *types.CachedTx, key types.TxKey, txInfo memp
 	if rsp.Code != abci.CodeTypeOK {
 		txmp.rejectedTxCache.Push(tx.Key(), rsp.Code)
 		txmp.metrics.FailedTxs.Add(1)
-		return rsp, fmt.Errorf("application rejected transaction with code %d (Log: %s)", rsp.Code, rsp.Log)
+		return rsp, nil
 	}
 
 	// Create wrapped tx

mempool/cat/pool_test.go

@@ -906,7 +906,7 @@ func TestTxMempool_TestRejectionIndexing(t *testing.T) {
 
 		// Try to add the transaction - it should be rejected
 		err := txmp.CheckTx(rejectedTx, nil, mempool.TxInfo{})
-		require.Error(t, err) // CheckTx returns an error for app rejection in CAT
+		require.NoError(t, err)
 		rejected, code = txmp.WasRecentlyRejected(txKey)
 		require.True(t, rejected)
 		require.Equal(t, uint32(101), code)