Deprecates redisbp for future version of baseplate.go

The baseplate.go/redisbp library does not support the latest Redis
cluster version (Redis 7+) as it is based on go-redis/v8. This
deprecates redisbp in favor of the go-redis/v9 redis client.

redis/db/redisbp/monitored_client.go

@@ -1,3 +1,9 @@
+// Package redisbp creates baseplate monitored Redis clients with go-redis/v8.
+// It supports only Redis <= 6.
+//
+// Deprecated: redisbp only supports only Redis 6. Use reddit-go/redisbp
+// to support Redis 6+ clients. This package will not be supported in the
+// future.
 package redisbp
 
 import (