Update Happo plugin description and link

We have merged the happo-cypress package into the main happo package, so
we need to update this link.

The repo can be found at https://github.com/happo/happo but since it
handles more than Cypress I thought it might make the most sense to link
to the Cypress integration documentation from this page.

I am also interested in getting the badge upgraded from community to
verified, but I assume that someone at Cypress will need to handle that. Let me know if I should open a PR for this!

Author: lencioni

src/data/plugins.json

@@ -934,8 +934,8 @@
         },
         {
           "name": "Happo",
-          "description": "Cross-platform, cross-browser screenshot testing for modern user interfaces.",
-          "link": "https://github.com/happo/happo-cypress",
+          "description": "Catch unexpected visual and accessibility changes and UI bugs",
+          "link": "https://docs.happo.io/docs/cypress",
           "keywords": ["screenshots", "visual regression"],
           "badge": "community"
         },