Update availability and limits

Co-authored-by: mia303 <[email protected]>

Author: RebeccaTamachiro

src/content/docs/secrets-store/manage-secrets/index.mdx

@@ -14,7 +14,7 @@ Once a secret is added to the Secrets Store, it can no longer be decrypted or ac
 
 ## Limits
 
-Customers enrolled in the closed beta can create up to 100 secrets per Cloudflare account.
+Customers who have created a Secrets Store in the open beta can create up to 20 secrets per account.
 
 ## Resources
 

src/content/plans/index.json

@@ -2922,7 +2922,7 @@
 		"properties": {
 			"availability": {
 				"title": "Availability",
-				"summary": "Available in closed beta",
+				"summary": "Available in open beta",
 				"free": "No",
 				"pro": "No",
 				"biz": "No",