Fix RTCStatsReport::ConstIterator move constructor.

This problem has been originally discovered by clang-tidy while trying
to apply performance-move-const-arg [1] on [2].

[1] - https://clang.llvm.org/extra/clang-tidy/checks/performance-move-const-arg.html
[2] - https://webrtc-review.googlesource.com/c/src/+/120350

Bug: webrtc:10252
Change-Id: I2b0a116f78ca8096a6cf2bc23e2f4b8f372ca04f
Reviewed-on: https://webrtc-review.googlesource.com/c/120815
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26512}
diff --git a/stats/rtc_stats_report.cc b/stats/rtc_stats_report.cc
index bdafd56..a56d30d 100644
--- a/stats/rtc_stats_report.cc
+++ b/stats/rtc_stats_report.cc
@@ -23,8 +23,7 @@
     StatsMap::const_iterator it)
     : report_(report), it_(it) {}
 
-RTCStatsReport::ConstIterator::ConstIterator(const ConstIterator&& other)
-    : report_(std::move(other.report_)), it_(std::move(other.it_)) {}
+RTCStatsReport::ConstIterator::ConstIterator(ConstIterator&& other) = default;
 
 RTCStatsReport::ConstIterator::~ConstIterator() {}