This annotation is used to permit routes defined by regexes instead of
simple prefix matching. This is used by our synapse deployment for
routing incomming HTTP requests to diffferent Synapse components.
I've stumbled upon this while deploying a new Matrix/Synapse instance.
This hasn't been yet a problem because the existing ingresses for Matrix
deployments predate admitomatic.
Change-Id: I821e58b214450ccf0de22d2585c3b0d11fbe71c0