bump web
bump web

concourse/concourse#1899

Submodule src/github.com/concourse/web 253b744a..1b71998e:
  > Update HD dashboard

Signed-off-by: Shash Reddy <1b59e0d2ac1ccc006e81da671242cb1775d373a2@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse