docs: fix two typos

Comments in test code.

router/tests/grpc.rs

@@ -175,7 +175,7 @@ async fn test_namespace_delete() {
         .expect("write failed");
     assert_eq!(response.status(), StatusCode::NO_CONTENT);
 
-    // The RPC endpoint must not return the namespace.
+    // The RPC endpoint must return a namespace.
     {
         let current = ctx
             .grpc_delegate()

service_grpc_namespace/src/lib.rs

@@ -284,7 +284,7 @@ mod tests {
                 retention_period_ns: Some(0), // A zero!
             }))
             .await
-            .expect("failed to create namespace")
+            .expect("failed to update namespace")
             .into_inner()
             .namespace
             .expect("no namespace in response");