Fixed wrong link in iframe.md

[korrectional]

https://jitsi.github.io/handbook/docs/dev-guide/dev-guide-iframe had a link to the react sdk documentation which was incorrect (https://jitsi.github.io/handbook/docs/dev-guide/dev-guide-iframe/dev-guide-react-sdk). I fixed the link (https://jitsi.github.io/handbook/docs/dev-guide/dev-guide-react-sdk/).

[damencho]

The link is relative to the current path and is working as expected in the handbook

[korrectional]

The link is relative to the current path and is working as expected in the handbook

When I am directed to https://jitsi.github.io/handbook/docs/dev-guide/dev-guide-iframe/dev-guide-react-sdk I see this: https://imgur.com/a/v8jRl1V
I tested this on both my phone and pc.

[damencho]

Hum, am I doing it wrong? I go to this page

And when I click the link for the tip about React SDK I'm forwarded to this page:

[saghul]

FWIW I get the same behavior as OP, aka page not found.

That said, the proposed fix is not good, it should be the document ID and docusaurus generates de right link. Unless there is a bug lurking somewhere...