Update CHANGELOG.md

Author: jon-batscha

CHANGELOG.md

@@ -21,7 +21,7 @@ NOTE: For more granular API-specific changes, please see our [API Changelog](htt
         $num_retries = 3, 
         $wait_seconds = 3,
         $guzzle_options = [],
-        $user_agent_suffix = "YOUR_APP_NAME");
+        $user_agent_suffix = "/YOUR_APP_NAME");
   ```
 
 ## [7.0.0] - revision 2024-02-15
@@ -239,4 +239,4 @@ For EmailMarketing:
   - client name: `Client` → `KlaviyoAPI`
   - Client variable name in readme examples: `$client` → `$klaviyo`
   - Some functions have changed name
-- Parameter ordering: The order of params has changed; you will need to update these for your existing implementation to work
+- Parameter ordering: The order of params has changed; you will need to update these for your existing implementation to work