system_wrappers: rename interface -> include

BUG=webrtc:5095
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1413333002 .

Cr-Commit-Position: refs/heads/master@{#10438}
diff --git a/webrtc/test/testsupport/fileutils.cc b/webrtc/test/testsupport/fileutils.cc
index c29e502..15abf5c 100644
--- a/webrtc/test/testsupport/fileutils.cc
+++ b/webrtc/test/testsupport/fileutils.cc
@@ -18,7 +18,7 @@
 #include <windows.h>
 #include <algorithm>
 
-#include "webrtc/system_wrappers/interface/utf_util_win.h"
+#include "webrtc/system_wrappers/include/utf_util_win.h"
 #define GET_CURRENT_DIR _getcwd
 #else
 #include <unistd.h>