Fix: use correct file parameter when uploading

Author: josiasmontag

src/main/java/com/cloudconvert/resource/AbstractImportFilesResource.java

@@ -320,6 +320,6 @@ protected HttpEntity getMultipartHttpEntity(
         final MultipartEntityBuilder multipartEntityBuilder = MultipartEntityBuilder.create().setContentType(ContentType.MULTIPART_FORM_DATA);
         uploadImportResponseResultForm.getParameters().forEach(multipartEntityBuilder::addTextBody);
         return new BufferedHttpEntity(multipartEntityBuilder.addPart(
-            FormBodyPartBuilder.create("form", new InputStreamBody(new BufferedInputStream(inputStream), filename)).build()).build());
+            FormBodyPartBuilder.create("file", new InputStreamBody(new BufferedInputStream(inputStream), filename)).build()).build());
     }
 }