pw_blob_store: Add missing include

This file uses uint32_t, but doesn't #include <cstdint>. For some
reason, this issue appears when migrating std::span to pw::span.

Change-Id: Idc59311c9662c36e5c3a6612521e2829674e5e41
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98100
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
diff --git a/pw_blob_store/public/pw_blob_store/internal/metadata_format.h b/pw_blob_store/public/pw_blob_store/internal/metadata_format.h
index 2d7a293..f63bbb1 100644
--- a/pw_blob_store/public/pw_blob_store/internal/metadata_format.h
+++ b/pw_blob_store/public/pw_blob_store/internal/metadata_format.h
@@ -14,6 +14,7 @@
 #pragma once
 
 #include <cstddef>
+#include <cstdint>
 
 #include "pw_preprocessor/compiler.h"