tools/http3_test: fix clippy warning

```
note: this value is dropped without further use
   --> src/lib.rs:277:31
    |
277 |             expect_resp_hdrs: expect_resp_hdrs.clone(),
    |                               ^^^^^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_clone
```

And

```
error: redundant field names in struct initialization
   --> src/lib.rs:277:13
    |
277 |             expect_resp_hdrs: expect_resp_hdrs,
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `expect_resp_hdrs`
    |
    = note: `-D clippy::redundant-field-names` implied by `-D warnings`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_field_names
error: aborting due to previous error
```
diff --git a/tools/http3_test/src/lib.rs b/tools/http3_test/src/lib.rs
index d7332e2..197f46b 100644
--- a/tools/http3_test/src/lib.rs
+++ b/tools/http3_test/src/lib.rs
@@ -274,7 +274,7 @@
             url: url.clone(),
             hdrs,
             body,
-            expect_resp_hdrs: expect_resp_hdrs.clone(),
+            expect_resp_hdrs,
             resp_hdrs: Vec::new(),
             resp_body: Vec::new(),
         }