Fix typo

Author: davidcauchi

book/src/libs/seth.md

@@ -350,7 +350,7 @@ pending_nonce_protection_enabled = true
 pending_nonce_protection_timeout = "5m"
 ```
 
-If you want to use HTTP instead of WS you can do so with by setting to true:
+If you want to use HTTP instead of WS you can do so by setting to true:
 
 ```toml
 force_http = false