fix: unit_present typo (#3461)

https://github.com/alibaba/canal/issues/3434

protocol/src/main/java/com/alibaba/otter/canal/protocol/CanalProtocol.proto

@@ -121,7 +121,7 @@ message Get {
     }
     //[default = 2]
     oneof unit_present {
-        int32 unit = 5;// 数字类型，0:纳秒,1:毫秒,2:微秒,3:秒,4:分钟,5:小时,6:天
+        int32 unit = 5;// 数字类型，0:纳秒,1:微秒,2:毫秒,3:秒,4:分钟,5:小时,6:天
     }
     //[default = false]
     oneof auto_ack_present {
@@ -151,4 +151,4 @@ message ClientRollback{
     string destination = 1;
     string client_id = 2;
     int64 batch_id = 3;
-}
+}