docs: Fix a few typos

[timgates42]

There are small typos in:

• docs/source/examples/related.rst
• docs/source/examples/serialise.rst
• examples/permissions.py
• stdnet/backends/redisb/init.py
• stdnet/odm/fields.py
• stdnet/odm/mapper.py
• stdnet/odm/search.py
• stdnet/odm/session.py
• stdnet/utils/test.py

Fixes:

• Should read shortcut rather than shurtcut.
• Should read false rather than falue.
• Should read through rather than throgh.
• Should read temporary rather than temorary.
• Should read straightforward rather than strightforward.
• Should read responsibility rather than responsability.
• Should read relationships rather than relationaships.
• Should read receiving rather than receving.

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