Modify env vars list for Lancebot and Python

[dawnofmidnight]

Both Python and Sir Lancebot had slightly outdated lists for environment variables, which were updated in this PR.

Changes

Python:
Add BOT_TRACE_LOGGERS
Remove REDDIT_CLIENT_ID and REDDIT_SECRET

Sir Lancebot:
Add REDDIT_CLIENT_ID, REDDIT_SECRET and REDDIT_WEBHOOK to the Token/APIs portion of the env var reference.

Preview:

Python:

Sir Lancebot:

[coveralls]

Coverage remained the same at 100.0% when pulling 0900c9e on dawnofmidnight:contributing-env-vars into 91cc514 on python-discord:main.

[ChrisLovering]

LGTM! Nice :D

[ToxicKidz]

Yep