mvcc: delete EXPIRE event type

Addressing https://github.com/coreos/etcd/pull/5484#discussion_r65005236.
etcd v3 doesn't expire keys. It's either PUT of DELETE.

mvcc/mvccpb/kv.pb.go

@@ -38,18 +38,15 @@ type Event_EventType int32
 const (
 	PUT    Event_EventType = 0
 	DELETE Event_EventType = 1
-	EXPIRE Event_EventType = 2
 )
 
 var Event_EventType_name = map[int32]string{
 	0: "PUT",
 	1: "DELETE",
-	2: "EXPIRE",
 }
 var Event_EventType_value = map[string]int32{
 	"PUT":    0,
 	"DELETE": 1,
-	"EXPIRE": 2,
 }
 
 func (x Event_EventType) String() string {
@@ -662,23 +659,23 @@ var (
 )
 
 var fileDescriptorKv = []byte{
-	// 285 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0xe2, 0xe2, 0xc8, 0x2e, 0xd3, 0x2b,
-	0x28, 0xca, 0x2f, 0xc9, 0x17, 0x62, 0xcb, 0x2d, 0x4b, 0x4e, 0x2e, 0x48, 0x92, 0x12, 0x49, 0xcf,
-	0x4f, 0xcf, 0x07, 0x0b, 0xe9, 0x83, 0x58, 0x10, 0x59, 0xa5, 0x75, 0x8c, 0x5c, 0x1c, 0xde, 0xa9,
-	0x95, 0x61, 0x89, 0x39, 0xa5, 0xa9, 0x42, 0x02, 0x5c, 0xcc, 0xd9, 0xa9, 0x95, 0x12, 0x8c, 0x0a,
-	0x8c, 0x1a, 0x3c, 0x41, 0x20, 0xa6, 0x90, 0x3a, 0x17, 0x7f, 0x72, 0x51, 0x6a, 0x62, 0x49, 0x6a,
-	0x7c, 0x51, 0x6a, 0x59, 0x66, 0x71, 0x66, 0x7e, 0x9e, 0x04, 0x13, 0x50, 0x96, 0x39, 0x88, 0x0f,
-	0x22, 0x1c, 0x04, 0x15, 0x15, 0x52, 0xe4, 0xe2, 0xc9, 0xcd, 0x4f, 0x41, 0xa8, 0x62, 0x06, 0xab,
-	0xe2, 0x06, 0x8a, 0xc1, 0x95, 0x48, 0x70, 0xb1, 0x97, 0xa5, 0x16, 0x81, 0x65, 0x59, 0xc0, 0xb2,
-	0x30, 0xae, 0x90, 0x08, 0x17, 0x6b, 0x19, 0xc8, 0x01, 0x12, 0xac, 0x60, 0x9b, 0x21, 0x1c, 0x90,
-	0x68, 0x4e, 0x6a, 0x62, 0x71, 0xaa, 0x04, 0x1b, 0x58, 0x35, 0x84, 0xa3, 0xd4, 0xc2, 0xc8, 0xc5,
-	0xea, 0x5a, 0x96, 0x9a, 0x57, 0x22, 0xa4, 0xcd, 0xc5, 0x52, 0x52, 0x59, 0x90, 0x0a, 0x76, 0x2e,
-	0x9f, 0x91, 0xb8, 0x1e, 0xc4, 0x9f, 0x7a, 0x60, 0x49, 0x08, 0x19, 0x02, 0x94, 0x0e, 0x02, 0x2b,
-	0x12, 0x52, 0xe0, 0x62, 0xca, 0x2e, 0x03, 0xbb, 0x9d, 0xdb, 0x48, 0x00, 0xa6, 0x14, 0xe6, 0xf1,
-	0x20, 0xa0, 0x9c, 0x92, 0x0e, 0x17, 0x27, 0x5c, 0x93, 0x10, 0x3b, 0x17, 0x73, 0x40, 0x68, 0x88,
-	0x00, 0x83, 0x10, 0x17, 0x17, 0x9b, 0x8b, 0xab, 0x8f, 0x6b, 0x88, 0xab, 0x00, 0x23, 0x88, 0xed,
-	0x1a, 0x11, 0xe0, 0x19, 0xe4, 0x2a, 0xc0, 0xe4, 0x24, 0x72, 0xe2, 0xa1, 0x1c, 0xc3, 0x05, 0x20,
-	0x3e, 0xf1, 0x48, 0x8e, 0xf1, 0x02, 0x10, 0x3f, 0x00, 0xe2, 0x24, 0x36, 0x70, 0xa0, 0x1a, 0x03,
-	0x02, 0x00, 0x00, 0xff, 0xff, 0x80, 0xae, 0xe6, 0x9d, 0x7e, 0x01, 0x00, 0x00,
+	// 274 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x44, 0x90, 0xc1, 0x4a, 0xc3, 0x40,
+	0x10, 0x86, 0xbb, 0x4d, 0x93, 0xd6, 0x69, 0xa9, 0x61, 0x09, 0xb8, 0x78, 0x28, 0x31, 0x17, 0x05,
+	0x21, 0x42, 0x7d, 0x03, 0x31, 0x27, 0x3d, 0xc8, 0x12, 0xbd, 0x4a, 0x1a, 0x87, 0x52, 0xd2, 0x76,
+	0x43, 0x1a, 0x17, 0xf3, 0x52, 0x3e, 0x47, 0x8f, 0x7d, 0x04, 0xf5, 0x49, 0xdc, 0xcc, 0x9a, 0x7a,
+	0x98, 0x65, 0xe6, 0xff, 0xfe, 0x65, 0xff, 0x59, 0x18, 0x15, 0x3a, 0x2e, 0x2b, 0x55, 0x2b, 0xee,
+	0x6d, 0x74, 0x9e, 0x97, 0x8b, 0xf3, 0x60, 0xa9, 0x96, 0x8a, 0xa4, 0x9b, 0xb6, 0xb3, 0x34, 0xfa,
+	0x64, 0x30, 0x7a, 0xc0, 0xe6, 0x25, 0x5b, 0xbf, 0x23, 0xf7, 0xc1, 0x29, 0xb0, 0x11, 0x2c, 0x64,
+	0x57, 0x13, 0xd9, 0xb6, 0xfc, 0x12, 0x4e, 0xf3, 0x0a, 0xb3, 0x1a, 0x5f, 0x2b, 0xd4, 0xab, 0xdd,
+	0x4a, 0x6d, 0x45, 0xdf, 0x50, 0x47, 0x4e, 0xad, 0x2c, 0xff, 0x54, 0x7e, 0x01, 0x93, 0x8d, 0x7a,
+	0xfb, 0x77, 0x39, 0xe4, 0x1a, 0x1b, 0xed, 0x68, 0x11, 0x30, 0xd4, 0x58, 0x11, 0x1d, 0x10, 0xed,
+	0x46, 0x1e, 0x80, 0xab, 0xdb, 0x00, 0xc2, 0xa5, 0x97, 0xed, 0xd0, 0xaa, 0x6b, 0xcc, 0x76, 0x28,
+	0x3c, 0x72, 0xdb, 0x21, 0xfa, 0x00, 0x37, 0xd1, 0xb8, 0xad, 0xf9, 0x35, 0x0c, 0xea, 0xa6, 0x44,
+	0x4a, 0x3b, 0x9d, 0x9f, 0xc5, 0x76, 0xcd, 0x98, 0xa0, 0x3d, 0x53, 0x83, 0x25, 0x99, 0x78, 0x08,
+	0xfd, 0x42, 0x53, 0xf4, 0xf1, 0xdc, 0xef, 0xac, 0xdd, 0xde, 0xd2, 0xb0, 0x28, 0x84, 0x93, 0xe3,
+	0x25, 0x3e, 0x04, 0xe7, 0xe9, 0x39, 0xf5, 0x7b, 0x1c, 0xc0, 0xbb, 0x4f, 0x1e, 0x93, 0x34, 0xf1,
+	0xd9, 0x5d, 0xb0, 0xff, 0x9e, 0xf5, 0x0e, 0xa6, 0xf6, 0x3f, 0x33, 0x76, 0x30, 0xf5, 0x65, 0x6a,
+	0xe1, 0xd1, 0x3f, 0xde, 0xfe, 0x06, 0x00, 0x00, 0xff, 0xff, 0x71, 0xd2, 0x34, 0xa9, 0x71, 0x01,
+	0x00, 0x00,
 }

mvcc/mvccpb/kv.proto

@@ -32,7 +32,6 @@ message Event {
   enum EventType {
     PUT = 0;
     DELETE = 1;
-    EXPIRE = 2;
   }
   // type is the kind of event. If type is a PUT, it indicates
   // new data has been stored to the key. If type is a DELETE,