Add link to Open-addresing wiki

PiperOrigin-RevId: 924993633
Change-Id: Ib405ec707e2d2ee87cd79192b6a8a1cc23b811d0

absl/container/internal/raw_hash_set.h

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 08ac8ac..4355e1f 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -13,6 +13,7 @@
 // limitations under the License.
 //
 // An open-addressing
+// [https://en.wikipedia.org/wiki/Open_addressing]
 // hashtable with quadratic probing.
 //
 // This is a low level hashtable on top of which different interfaces can be