system_wrappers: Fix include header guards.

This should have been a part of https://codereview.webrtc.org/1413333002/

The header guard PRESUBMIT rule is being enabled in
https://codereview.webrtc.org/1419203005 so things like this won't
happen in the future.

BUG=5095
NOTRY=True

Review URL: https://codereview.webrtc.org/1425693005

Cr-Commit-Position: refs/heads/master@{#10475}
diff --git a/webrtc/system_wrappers/include/stringize_macros.h b/webrtc/system_wrappers/include/stringize_macros.h
index ab8c43d..9c8e7e9 100644
--- a/webrtc/system_wrappers/include/stringize_macros.h
+++ b/webrtc/system_wrappers/include/stringize_macros.h
@@ -15,8 +15,8 @@
 // symbols (or their output) and manipulating preprocessor symbols
 // that define strings.
 
-#ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_STRINGIZE_MACROS_H_
-#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_STRINGIZE_MACROS_H_
+#ifndef WEBRTC_SYSTEM_WRAPPERS_INCLUDE_STRINGIZE_MACROS_H_
+#define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_STRINGIZE_MACROS_H_
 
 // This is not very useful as it does not expand defined symbols if
 // called directly. Use its counterpart without the _NO_EXPANSION
@@ -35,4 +35,4 @@
 //   STRINGIZE(B(y)) produces "myobj->FunctionCall(y)"
 #define STRINGIZE(x) STRINGIZE_NO_EXPANSION(x)
 
-#endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_STRINGIZE_MACROS_H_
+#endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_STRINGIZE_MACROS_H_