1.4 deprecated operators are not supported correctly

SQLAlchemy 1.4 release notes:
https://docs.sqlalchemy.org/en/14/changelog/changelog_14.html#change-8dd50c1cc4d512bf97b23fb0243619af

```
Several operators are renamed to achieve more consistent naming across SQLAlchemy.

The operator changes are:
isfalse is now is_false
isnot_distinct_from is now is_not_distinct_from
istrue is now is_true
notbetween is now not_between
notcontains is now not_contains
notendswith is now not_endswith
notilike is now not_ilike
notlike is now not_like
notmatch is now not_match
notstartswith is now not_startswith
nullsfirst is now nulls_first
nullslast is now nulls_last
isnot is now is_not
not_in_ is now not_in
```

Stubs needs to be updated:
```
Module "sqlalchemy.sql.expression" has no attribute "nulls_last"; maybe "nullslast"?
```

Version:
```
Successfully installed sqlalchemy-stubs-0.4
```