docs(upstash): update Standard plan description for Redis to clarify replica region pricing

Author: yphus

upstash/redis.html.md

@@ -148,7 +148,7 @@ Upstash also offers fixed price plans for when:
 These fixed price plans are available via `flyctl redis update <dbname>`:
 
 * Starter: $10 per month, single region only. Includes 200MB storage, 100 req/sec
-* Standard: $50 per month, per region. Includes 3GB storage, 100 req/sec
+* Standard: $50 per month, $10 per replica region. Includes 3GB storage, 100 req/sec
 * Pro 2K: $280 per month, $100 per replica region. Includes 50GB storage, 10k req/sec
 
 Your usage is updated hourly on your monthly Fly.io bill. You can track database usage details in the [Upstash web console](#the-upstash-web-console) as well.