Some out of date wiki information

[qstokkink]

The wiki section overlay protocol for synchronization is out of date: https://github.com/Tribler/tribler/wiki#overlay-protocol-for-synchronization

This still mentions Dispersy as our main messaging infrastructure and links to my personal fork of IPv8 as a "new overlay".

We can still keep the description of Dispersy for historic reasons, but we should update this section to better reflect the current architecture of Tribler.

Lastly, the "Tribler history" section (https://github.com/Tribler/tribler/wiki#tribler-history) mentions the release of IPv8 in 2019. Actually IPv8 was first released in october 2017 (the attestation layer in december 2017), first deployed in Tribler in 2018 (deprecating Dispersy) and we fully switched all Tribler communication to IPv8 in 2019.