[base] Add missing include in template-utils.h

{std::ostream} was used without including either <ostream> or <iosfwd>.

R=ahaas@chromium.org

Change-Id: I92facf672c81a17e2ff24658bbefd961b4f4d445
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248196Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68385}

src/base/template-utils.h

@@ -7,6 +7,7 @@
 
 #include <array>
 #include <functional>
+#include <iosfwd>
 #include <type_traits>
 #include <utility>