Fix typo in example code snippet.

PiperOrigin-RevId: 610672905
Change-Id: I8e4ae98bb6e6421540a3073e3e6cb7de60fd32a9
diff --git a/absl/base/prefetch.h b/absl/base/prefetch.h
index eb40a44..482cde3 100644
--- a/absl/base/prefetch.h
+++ b/absl/base/prefetch.h
@@ -129,7 +129,7 @@
 //
 //  void* Arena::Allocate(size_t size) {
 //    void* ptr = AllocateBlock(size);
-//    absl::PrefetchToLocalCacheForWrite(p);
+//    absl::PrefetchToLocalCacheForWrite(ptr);
 //    return ptr;
 //  }
 //