Fix record.update contract, remove trailing spaces
"%m
= fun field r => %record_remove% field r,
- update | forall a. Str -> a -> { ; a} -> { ; a}
+ update | forall a. Str -> a -> {_: a} -> {_: a}
| doc m%"
Update a field of a record with a new value. `update` doesn't mutate the
original record but returns a new one instead. If the field to update is absent
