[docs] Add note about txids to signature status RPC method docs (#31628)

docs/src/api/methods/_getSignatureStatuses.mdx

@@ -12,7 +12,7 @@ import {
 
 ## getSignatureStatuses
 
-Returns the statuses of a list of signatures.
+Returns the statuses of a list of signatures. Each signature must be a [txid](/terminology#transaction-id), the first signature of a transaction.
 
 :::info
 Unless the `searchTransactionHistory` configuration parameter is included,

docs/src/api/websocket/_signatureSubscribe.mdx

@@ -13,6 +13,7 @@ import {
 ## signatureSubscribe
 
 Subscribe to a transaction signature to receive notification when a given transaction is committed. On `signatureNotification` - the subscription is automatically cancelled.
+The signature must be a [txid](/terminology#transaction-id), the first signature of a transaction.
 
 <DocSideBySide>
 <CodeParams>