pw_result: Fix typo in template member

An internal compiler upgrade surfaced this error. See cl/633159698.

Bug: 339794389
Change-Id: Ic5e28cd24e5f3a6c8aa04023a9bbebc9a186e833
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/209667
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Pigweed-Auto-Submit: Ted Pudlik <tpudlik@google.com>
Reviewed-by: Carlos Chinchilla <cachinchilla@google.com>
Commit-Queue: Ted Pudlik <tpudlik@google.com>
diff --git a/pw_result/public/pw_result/internal/expected_impl.h b/pw_result/public/pw_result/internal/expected_impl.h
index fe97010..3288016 100644
--- a/pw_result/public/pw_result/internal/expected_impl.h
+++ b/pw_result/public/pw_result/internal/expected_impl.h
@@ -769,7 +769,7 @@
   constexpr expected& operator=(expected&& rhs) noexcept(
       std::is_nothrow_move_constructible_v<E> &&
       std::is_nothrow_move_assignable_v<E>) {
-    error_contents_ = std::move(rhs.error_contents);
+    error_contents_ = std::move(rhs.error_contents_);
     return *this;
   }
   template <class G>