Fix payload attributes json (#12169)

Co-authored-by: terencechain <terence@prysmaticlabs.com>

beacon-chain/rpc/apimiddleware/structs.go

@@ -1185,7 +1185,7 @@ type EventPayloadAttributeV2Json struct {
 	ParentBlockNumber string                   `json:"parent_block_number"`
 	ParentBlockRoot   string                   `json:"parent_block_root" hex:"true"`
 	ParentBlockHash   string                   `json:"parent_block_hash" hex:"true"`
-	PayloadAttributes *PayloadAttributesV2Json `json:"payload_attributes_v2"`
+	PayloadAttributes *PayloadAttributesV2Json `json:"payload_attributes"`
 }
 
 type PayloadAttributesV1Json struct {

beacon-chain/rpc/eth/events/events.go

@@ -331,7 +331,7 @@ func (s *Server) streamPayloadAttributes(stream ethpbservice.Events_StreamEvents
 				ParentBlockNumber: headPayload.BlockNumber(),
 				ParentBlockRoot:   headRoot,
 				ParentBlockHash:   headPayload.BlockHash(),
-				PayloadAttributesV2: &enginev1.PayloadAttributesV2{
+				PayloadAttributes: &enginev1.PayloadAttributesV2{
 					Timestamp:             uint64(t.Unix()),
 					PrevRandao:            prevRando,
 					SuggestedFeeRecipient: headPayload.FeeRecipient(),

beacon-chain/rpc/eth/events/events_test.go

@@ -494,7 +494,7 @@ func TestStreamEvents_StateEvents(t *testing.T) {
 				ParentBlockNumber: 1,
 				ParentBlockRoot:   make([]byte, 32),
 				ParentBlockHash:   make([]byte, 32),
-				PayloadAttributesV2: &enginev1.PayloadAttributesV2{
+				PayloadAttributes: &enginev1.PayloadAttributesV2{
 					Timestamp:             24,
 					PrevRandao:            prevRando,
 					SuggestedFeeRecipient: make([]byte, 20),

proto/eth/v1/events.proto

@@ -159,6 +159,6 @@ message EventPayloadAttributeV2 {
         // The version N must match the payload attributes for the hard fork matching version.
         // The beacon API encoded object must have equivalent fields to its counterpart in execution-apis with two differences:
         // 1) snake_case identifiers must be used rather than camelCase; 2) integers must be encoded as quoted decimals rather than big-endian hex.
-        engine.v1.PayloadAttributesV2 payload_attributes_v2 = 8;
+        engine.v1.PayloadAttributesV2 payload_attributes = 8;
   }
 }