message: Fix observer ref counting.
  By calling release() the ref counter is not decremented and when the
  observer is later wrapped in a scoped_refprt its counter will be 2
  instead of 1, leading to a memory leak.
  Cr-Commit-Position: refs/heads/main@{#36862}
diff: @@ -68,7 +68,7 @@ class TestPeer final {
  void CreateOffer(
  rtc::scoped_refptr<CreateSessionDescriptionObserver> observer) {
  RTC_CHECK(wrapper_) << "TestPeer is already closed";
  - pc()->CreateOffer(observer.release(), params_.rtc_offer_answer_options);
  + pc()->CreateOffer(observer.get(), params_.rtc_offer_answer_options);
  }
  std::unique_ptr<SessionDescriptionInterface> CreateOffer() {
  RTC_CHECK(wrapper_) << "TestPeer is already closed";
  