misc: restore sniffing of csv dialect (#44016)

This reverts commit 586f322eba, "python3:
explicit delimiter and quotechar in csv import (#28276)".

src/authentic2/csv_import.py

@@ -182,8 +182,7 @@ class CsvImporter(object):
             if not dialect:
                 self.error = Error('unknown-csv-dialect', _('Unknown CSV dialect'))
                 return False
-            reader = UnicodeReader(
-                    input_fd, dialect, delimiter=str(','), quotechar=str('"'))
+            reader = UnicodeReader(input_fd, dialect)
             self.rows = list(reader)
             return True