Fix warnings from Clippy v1.50.0 (nightly). (#58)

Signed-off-by: Piotr Sikora <[email protected]>

examples/http_body.rs

@@ -60,7 +60,7 @@ impl HttpContext for HttpBody {
         // Since we returned "Pause" previuously, this will return the whole body.
         if let Some(body_bytes) = self.get_http_response_body(0, body_size) {
             let body_str = String::from_utf8(body_bytes).unwrap();
-            if body_str.find("secret").is_some() {
+            if body_str.contains("secret") {
                 let new_body = format!("Original message body ({} bytes) redacted.", body_size);
                 self.set_http_response_body(0, body_size, &new_body.into_bytes());
             }