chore(readme): remove non-needed mut in boolean example

README.md

@@ -68,7 +68,7 @@ use tfhe::boolean::prelude::*;
 
 fn main() {
     // We generate a set of client/server keys, using the default parameters:
-    let (mut client_key, mut server_key) = gen_keys();
+    let (client_key, server_key) = gen_keys();
 
     // We use the client secret key to encrypt two messages:
     let ct_1 = client_key.encrypt(true);