Sort #includes that got unsorted when gmock.h and gtest.h moved to webrtc/test/

gmock.h and gtest.h were moved (or rather, got wrappers so that we
could put some icky compatibility hacks in one place instead of 500)
in this CL: https://codereview.webrtc.org/2358993004/

NOPRESUBMIT=true
BUG=webrtc:6398

Review-Url: https://codereview.webrtc.org/2381013002
Cr-Commit-Position: refs/heads/master@{#14464}
diff --git a/webrtc/api/proxy_unittest.cc b/webrtc/api/proxy_unittest.cc
index 8c16513..193fb29 100644
--- a/webrtc/api/proxy_unittest.cc
+++ b/webrtc/api/proxy_unittest.cc
@@ -13,10 +13,10 @@
 #include <memory>
 #include <string>
 
-#include "webrtc/test/gmock.h"
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/refcount.h"
 #include "webrtc/base/thread.h"
+#include "webrtc/test/gmock.h"
 
 using ::testing::_;
 using ::testing::DoAll;