Communicate PRR freeze

Author: gracenng

sig-architecture/production-readiness.md

@@ -20,6 +20,10 @@ As of 1.21, PRRs are now blocking. PRR _approval_ is required for the enhancemen
 to be part of the release. This means that any KEPs targeting the release for any
 stage will require production readiness approval by the *Enhancements Freeze Date*.
 
+Introduced in 1.23, *Product Readiness Freeze* happens a week before *Enhancements Freeze Date*. All KEPs must be opted in by this date to help PRR reviewers provision their workload. 
+KEPs opted in after the *Product Readiness Freeze* are at risk
+of not being reviewed by the PRR team, depending on bandwidth.
+
 Note that some of the questions in the [KEP template] should be answered in both
 the KEP's README.md and the `kep.yaml`, in order to support automated checks on
 the PRR. The template points out these as needed.