Prefer {byte,wide}string.h inclusion over fx_string.h

Most files only care to operate on one string type, so we can halve the
inclusions that fx_string.h would provide.

Change-Id: I1dcbb008af9ee31c9151051b0505cb62cd451802
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/87310
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/fxbarcode/cbc_qrcode.h b/fxbarcode/cbc_qrcode.h
index a015858..4ad658c 100644
--- a/fxbarcode/cbc_qrcode.h
+++ b/fxbarcode/cbc_qrcode.h
@@ -7,7 +7,7 @@
 #ifndef FXBARCODE_CBC_QRCODE_H_
 #define FXBARCODE_CBC_QRCODE_H_
 
-#include "core/fxcrt/fx_string.h"
+#include "core/fxcrt/widestring.h"
 #include "fxbarcode/cbc_codebase.h"
 
 class CBC_QRCodeWriter;