docs: Fix a few typos

[timgates42]

There are small typos in:

• src/dal/forms.py
• src/dal/test/stories.py
• src/dal_queryset_sequence/fields.py
• src/dal_select2_queryset_sequence/views.py

Fixes:

• Should read necessarily rather than necessarely.
• Should read submitted rather than submited.
• Should read imprecise rather than unprecise.
• Should read different rather than diffrent.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

[jpic]

Thanks!