Fix typo in expiration endpoint documentation

Corrected the documentation to reflect the correct delete key parameter instead of the incorrect download key parameter for the expiration endpoint. Updated the example curl command to use a valid delete key format.

README.md

@@ -105,10 +105,10 @@ curl --request GET 'http://localhost:3000/expiration/db6186c8795740379d26fc61ecb
 
 ### Set file expiration
 
-**PUT `INSTANCE_URL/expiration/:download_key/:expiration`**: set the file expiration date
+**PUT `INSTANCE_URL/expiration/:delete_key/:expiration`**: set the file expiration date
 
 ```sh
-curl --request PUT 'http://localhost:3000/expiration/db6186c8795740379d26fc61ecba1a24/2717940582741'
+curl --request PUT 'http://localhost:3000/expiration/11561161dffe4a1298992ce063be5ff9/2717940582741'
 ```
 
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