chore: fix a warning for gpu strings

- we don't currently have strings on GPU and so don't run clippy for them

tfhe/src/high_level_api/strings/ascii/mod.rs

@@ -297,6 +297,7 @@ impl crate::integer::gpu::ciphertext::compressed_ciphertext_list::CudaExpandable
         blocks: crate::integer::gpu::ciphertext::CudaRadixCiphertext,
         kind: DataKind,
     ) -> crate::Result<Self> {
+        let _ = (blocks, kind);
         Err(crate::error!("GPU does not supports strings yet"))
     }
 }