Link for "W3C Horizontal Groups" doesn't describe W3C horizontal groups

[jyasskin]

https://www.w3.org/2023/Process-20230612/#WGCharter, https://www.w3.org/2023/Process-20230612/#wide-review, and https://www.w3.org/2023/Process-20230612/#streamlined-update have a W3C Horizontal Groups link, but https://www.w3.org/Guide/process/charter.html#horizontal-review doesn't describe any horizontal groups anymore. It also only addresses horizontal review of charters, while the Process requires horizontal review of specs too.

[samuelweiler]

See also https://github.com/w3c/w3process/pull/541#issuecomment-879841040

Is this a regression?

[fantasai]

@plehegar Is there an appropriate link target for this concept? (If not we need to create one somewhere.)