PR #1692: Add missing `<utility>` include

Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/1692

`optimization.h` uses `std::unreachable()` if available but does not include `<utility>`, causing errors in `absl/strings/ascii.cc`.
Merge bf912bb4e38341d6152ee145ec2be00251c42552 into 8a28a0c8732ba3bf0191fb6292fcad6e5948a047

Merging this change closes #1692

COPYBARA_INTEGRATE_REVIEW=https://github.com/abseil/abseil-cpp/pull/1692 from poconn:optimization_missing_include bf912bb4e38341d6152ee145ec2be00251c42552
PiperOrigin-RevId: 645643983
Change-Id: I3966984afa81f2f6bce65dd872d326f0af114bfa
diff --git a/absl/base/optimization.h b/absl/base/optimization.h
index f985995..fb7ac37 100644
--- a/absl/base/optimization.h
+++ b/absl/base/optimization.h
@@ -23,6 +23,7 @@
 #define ABSL_BASE_OPTIMIZATION_H_
 
 #include <assert.h>
+#include <utility>
 
 #include "absl/base/config.h"
 #include "absl/base/options.h"