[fuzzers] Fix warnings (#34630)

test/core/end2end/fuzzers/fuzzing_common.cc

@@ -757,7 +757,7 @@ void BasicFuzzer::TryShutdown() {
 }
 
 void BasicFuzzer::Run(absl::Span<const api_fuzzer::Action* const> actions) {
-  int action_index = 0;
+  size_t action_index = 0;
   auto allow_forced_shutdown = std::make_shared<bool>(false);
   auto no_more_actions = [&]() { action_index = actions.size(); };
 

test/core/end2end/fuzzers/server_fuzzer.cc

@@ -81,10 +81,11 @@ class ServerFuzzer final : public BasicFuzzer {
 
  private:
   Result CreateChannel(
-      const api_fuzzer::CreateChannel& create_channel) override {
+      const api_fuzzer::CreateChannel& /* create_channel */) override {
     return Result::kFailed;
   }
-  Result CreateServer(const api_fuzzer::CreateServer& create_server) override {
+  Result CreateServer(
+      const api_fuzzer::CreateServer& /* create_server */) override {
     return Result::kFailed;
   }
   void DestroyServer() override {