use 'postgres' driver (not postgresql). Include plain url to guide

[cdecker]

Apologies @lightningorb, I have no idea what happened to #5521, so I'm reopening the PR with this amended changeset.

[lightningorb]

@cdecker thanks for including that tinyurl link. This looks good.

I didn't want to give up on the issue so tried building sphinx docs locally, and the .md link was fine. I then created an RTD of my branch (had to create a .readthedocs.yaml) however the issue was still taking place. I poked around in sphinx for a bit but gave up as i can't repro the issue here.

[cdecker]

Yep, RTD assuming that links ending in .md seems to be a common occurence, and the short URL should avoid that issue by sidestepping it. It's a bit less clean than fixing the root cause, but we're not sphinx or RTD devs so let them figure this out ^^