update std.heap.page_allocator to std.testing.allocator in hash_map.zig

lib/std/hash_map.zig

@@ -1833,15 +1833,15 @@ test "put and remove loop in random order" {
 test "remove many elements in random order" {
     const Map = AutoHashMap(u32, u32);
     const n = 1000 * 100;
-    var map = Map.init(std.heap.page_allocator);
+    var map = Map.init(std.testing.allocator);
     defer map.deinit();
 
     var keys: std.ArrayList(u32) = .empty;
-    defer keys.deinit(std.heap.page_allocator);
+    defer keys.deinit(std.testing.allocator);
 
     var i: u32 = 0;
     while (i < n) : (i += 1) {
-        keys.append(std.heap.page_allocator, i) catch unreachable;
+        keys.append(std.testing.allocator, i) catch unreachable;
     }
 
     var prng = std.Random.DefaultPrng.init(std.testing.random_seed);