Fix links redirecting to powsybl website documentation

[colinepiloquet]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines

Does this PR already have an issue describing the problem?

No

What kind of change does this PR introduce?

Docs update

What is the current behavior?

Some links refer to powysbl.org documentation that has been deleted.

What is the new behavior (if this is a feature change)?
Replaced by readthedocs website. However, I didn't manage to use Intersphinx...

Does this PR introduce a breaking change or deprecate an API?

• Yes
• No

[HugoKulesza]

@colinepiloquet I think there is one left on index.rst when I search for powsybl.org in the code (and 5 more in image metadata but I don't know what they're used for)

[colinepiloquet]

@colinepiloquet I think there is one left on index.rst when I search for powsybl.org in the code (and 5 more in image metadata but I don't know what they're used for)

I think it's ok to leave it in the index.rst, to have a link to the main website somewhere in the introduction.
In the metadata I think it's normal, it comes with the generation of the svg. @So-Fras can you confirm?

[So-Fras]

I think that it is okay to link to the main website in the index.rst, especially since we added a direct link to the readthedocs documentation. As for the svg files, we can leave it as it is for now.