bpo-44704: Make Set._hash consistent with frozenset.__hash__ (GH-27281) (GH-27282)

diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index d92b848..bff58ad 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -696,6 +696,7 @@ def _hash(self):
             hx = hash(x)
             h ^= (hx ^ (hx << 16) ^ 89869747)  * 3644798167
             h &= MASK
+        h ^= (h >> 11) ^ (h >> 25)
         h = h * 69069 + 907133923
         h &= MASK
         if h > MAX: