Add missing #include

Change-Id: I7d282e1329d229200706801d0a4f941bae3c15df
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/83727
Auto-Submit: Lily Chen <chlily@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: Lily Chen <chlily@google.com>
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/span.h

diff --git a/include/openssl/span.h b/include/openssl/span.h
index 11798a7..3b48dda 100644
--- a/include/openssl/span.h
+++ b/include/openssl/span.h
@@ -24,6 +24,7 @@
 #include <stdlib.h>
 
 #include <algorithm>
+#include <array>
 #include <limits>
 #include <string_view>
 #include <type_traits>