closes bpo-37446: resolve undefined behavior in Python/hamt.c (GH-17727)

(cherry picked from commit d0c92e81aa2171228a23cb2bed36f7dab975257d)

Co-authored-by: Batuhan Taşkaya <47358913+isidentical@users.noreply.github.com>
diff --git a/Python/hamt.c b/Python/hamt.c
index 3841259..5efc8d7 100644
--- a/Python/hamt.c
+++ b/Python/hamt.c
@@ -1864,7 +1864,7 @@
                     continue;
                 }
 
-                bitmap |= 1 << i;
+                bitmap |= 1U << i;
 
                 if (IS_BITMAP_NODE(node)) {
                     PyHamtNode_Bitmap *child = (PyHamtNode_Bitmap *)node;