Add "environment.deploy" activity on "Activity reference" page

[nicogommen]

Where on fixed.docs.upsun.com should be changed?

https://docs.upsun.com/integrations/activity/reference.html#environment-activity-types https://fixed.docs.upsun.com/integrations/activity/reference.html#environment-activity-types

What exactly should be updated?

For manual deployments, we now have a new environment.deploy activity that we should add in the "environment activity types" table.

Additional context

No response

[flovntp]

related #5083 --> missing environment.alert