docs: fix a few simple typos

[timgates42]

There are small typos in:

• CONTRIBUTING.md
• docs/development.rst
• docs/index.rst
• docs/logging.rst
• docs/pubsub.rst
• docs/upgrading.rst
• rediscluster/client.py
• rediscluster/connection.py
• tests/test_cluster_node_manager.py
• tests/test_commands.py
• tests/test_encoding_cluster.py

Fixes:

• Should read specified rather than specefied.
• Should read implementation rather than impelmentation.
• Should read upstream rather than uptream.
• Should read iterate rather than itterate.
• Should read recommended rather than reccommended.
• Should read received rather than recieved.
• Should read preferred rather than preffered.
• Should read possibility rather than posiblity.
• Should read interval rather than intervall.
• Should read examples rather than exmaples.
• Should read documentation rather than documentaion.

Closes #461

[holmboe]

Nice contribution!

[Grokzen]

@timgates42 Thank you for these fixes :)