Address 4590

Correct typo.

Author: JorjMcKie

src/utils.py

@@ -4369,7 +4369,7 @@ def remove_hidden(cont_lines):
         found_redacts = False
         for annot in page.annots():
             if annot.type[0] == mupdf.PDF_ANNOT_FILE_ATTACHMENT and attached_files:
-                annot.update_file(buffer=b" ")  # set file content to empty
+                annot.update_file(buffer_=b" ")  # set file content to empty
             if reset_responses:
                 annot.delete_responses()
             if annot.type[0] == pymupdf.PDF_ANNOT_REDACT:  # pylint: disable=no-member