HttpProxyMapperTest: cleanup (#32572)

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test/core/client_channel/http_proxy_mapper_test.cc

@@ -16,8 +16,6 @@
 //
 //
 
-#include <string>
-
 #include "absl/types/optional.h"
 #include "gtest/gtest.h"
 
@@ -64,7 +62,6 @@ TEST(NoProxyTest, Basic) {
 TEST(NoProxyTest, EmptyEntries) {
   ScopedSetEnv no_proxy("foo.com,,google.com,,");
   auto args = ChannelArgs().Set(GRPC_ARG_HTTP_PROXY, "http://proxy.google.com");
-  absl::optional<std::string> name_to_resolve;
   EXPECT_EQ(HttpProxyMapper().MapName("dns:///test.google.com:443", &args),
             absl::nullopt);
   EXPECT_EQ(args.GetString(GRPC_ARG_HTTP_CONNECT_SERVER), absl::nullopt);