pw_span: Fixes bazel build allowing <span> polyfill

This adds the public_overrides directory to the includes.
This allows for you to include using `#include <span>`
rather than `#include "pw_span/span.h"`.

Change-Id: I0094bdbf69b6701f338110a6c563e2144f81e192
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/30080
Commit-Queue: Wyatt Hepler <hepler@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
Reviewed-by: Akira Baruah <akira.baruah@gmail.com>
diff --git a/pw_span/BUILD b/pw_span/BUILD
index 7b242ff..6788a6b 100644
--- a/pw_span/BUILD
+++ b/pw_span/BUILD
@@ -26,7 +26,10 @@
     name = "pw_span",
     srcs = ["public/pw_span/internal/span.h"],
     hdrs = ["public_overrides/span"],
-    includes = ["public"],
+    includes = [
+        "public",
+        "public_overrides",
+    ],
     deps = ["//pw_polyfill"],
 )