Revert "write_records_to_tsv: Stop quoting output TSV"

This reverts commit 915672e.

Per discussion in <#1563 (comment)>,
keep CSV-like TSV where quotes may be added or removed, but parsed
values should be equivalent.

augur/io/metadata.py

@@ -548,9 +548,7 @@ def write_records_to_tsv(records, output_file):
             output_columns,
             extrasaction='ignore',
             delimiter='\t',
-            lineterminator='\n',
-            quoting=csv.QUOTE_NONE,
-            quotechar=None,
+            lineterminator='\n'
         )
         tsv_writer.writeheader()
         tsv_writer.writerow(first_record)

tests/io/test_metadata.py

@@ -458,7 +458,7 @@ def output_records():
 def expected_output_tsv():
     return (
         "strain\tcountry\tdate\n"
-        'SEQ_A\t"USA"\t2020-10-01\n'
+        'SEQ_A\t"""USA"""\t2020-10-01\n'
         "SEQ_T\tUSA\t2020-10-02\n"
     )