Only add newlines after keys

After comments they are included in the string

authorizedkeys/parser.py

@@ -72,5 +72,5 @@ def dump_file(keys: list[AuthorizedKey | str], f: IO[str]) -> None:
 	for rec in keys:
 		if isinstance(rec, AuthorizedKey):
 			rec = rec.to_string()
+			rec += '\n'
 		f.write(rec)
-		f.write('\n')