Merge pull request #7 from larksuite/feat/attachment_mime_type_0513

remove unused name

Author: heguiyan

src/main/java/com/lark/project/service/attachment/builder/UploadAttachmentReqBody.java

@@ -9,7 +9,6 @@ public class UploadAttachmentReqBody {
     @SerializedName("file")
     private File file;
 
-    @SerializedName("file")
     private String mimeType;
 
     @SerializedName("field_key")