IWYU: uint32_t requires stdint.h include in printing PageRange.

Fix this error:
../../printing/page_range.h:20:3: error: ‘uint32_t’ does not name a type

Introduced in this commit:
https://chromium-review.googlesource.com/c/chromium/src/+/2351580

Bug: 951519
Change-Id: I0c86cfc5dc711b062021dd8661d27d6442e7d47d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2423909
Commit-Queue: José Dapena Paz <jdapena@igalia.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809758}

printing/page_range.h

@@ -5,6 +5,8 @@
 #ifndef PRINTING_PAGE_RANGE_H_
 #define PRINTING_PAGE_RANGE_H_
 
+#include <stdint.h>
+
 #include <vector>
 
 #include "printing/printing_export.h"