Fix JWT/exp typo

Author: lcrilly

opaque_session_token/README.md

@@ -26,7 +26,7 @@ Each of the `keyval_zone` parameters are described below.
 
  * **state** (optional) - Specifies where all of the ID Tokens in the key-value store are saved, so that sessions will persist across restart or reboot of the NGINX host. The NGINX Plus user account, typically **nginx**, must have write permission to the directory where the state file is stored. Consider creating a dedicated directory for this purpose.
 
- * **timeout** - Expired tokens are removed from the key-value store after the `timeout` value. This should be set to value slightly longer than the JWT validity period. JWT validation occurs on each request, and will fail when the expiry date (`exp` claim) has elapsed. If JWTs are issued without a JWT then set `timeout` to the desired session duration. If JWTs are issued with various validity periods then set `timeout` to exceed the longest period.
+ * **timeout** - Expired tokens are removed from the key-value store after the `timeout` value. This should be set to value slightly longer than the JWT validity period. JWT validation occurs on each request, and will fail when the expiry date (`exp` claim) has elapsed. If JWTs are issued without an `exp` claim then set `timeout` to the desired session duration. If JWTs are issued with a range of validity periods then set `timeout` to exceed the longest period.
 
  * **sync** (optional) - If deployed in a cluster, the key-value store may be synchronized across all instances in the cluster, so that all instances are able to create and validate authenticated sessions. Each instance must be configured to participate in state sharing with the [zone_sync module](http://nginx.org/en/docs/stream/ngx_stream_zone_sync_module.html) and by adding the `sync` parameter to the `keyval_zone` directive above.