[fix][CD] Add env var for workflows backend

[himanshu-bhandoh]

Adds workflows backend host env var to temporal worker

[roberto-retool]

it looks like we actually may not need changes here. The file you're changing is for the temporal server's worker. It looks like we may already set this for the retool temporal worker since we set it in aws_ecs/locals.tf and bring those envvars in the ecs task definition

terraform-retool-modules/modules/aws_ecs/main.tf

Line 405 in b1340f0

local.environment_variables,