(Temporarily) fix stable docs link in README.md

[jacobusmmsmit]

246 pointed out that the docs are not correctly deployed. Unfortunately, this is still the case so in the meantime a quick "bandaid" fix which makes the stable docs accessible is just to change the stable docs link.

Right now the stable docs are hard to find unless you know that removing /stable from the url goes there.

Apologies if this is the wrong fix to the problem, it was just bugging me.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (c982cde) 81.53% compared to head (0b17192) 81.53%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #249 +/- ## ======================================= Coverage 81.53% 81.53% ======================================= Files 18 18 Lines 1587 1587 ======================================= Hits 1294 1294 Misses 293 293 ```

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[devmotion]

This PR has to be reverted. The new link points to completely outdated docs. IMO a broken link is better than one to incorrect docs.

[gdalle]

Okay, but is there a link to the current stable docs? Sorry for merging but I thought this was the right one too, given that it is close to the current URL. So I have in fact used the orange site as a stable docs

[devmotion]

It's some docs from years ago. The link was removed on purpose in #246.