[6.0][python] Replace deprecated assertEquals with assertEqual in build graph test

`unitest.assertEquals` is deprecated in Python 3.2 and finally removed in
Python 3.12 [1]. Due to this, this test files in recent Linux distros,
like Ubuntu 24.04 or Fedora 38+. This patch replaces the deprecated
function with `assertEqual`.

[1] https://docs.python.org/3/whatsnew/3.12.html

(cherry picked from commit c31f1f5)

Author: bc-lee

utils/swift_build_support/tests/test_build_graph.py

@@ -54,4 +54,4 @@ def test_simple_build_graph(self):
         selectedProducts = [products['swiftpm']]
         schedule = build_graph.produce_scheduled_build(selectedProducts)
         names = [x.name for x in schedule[0]]
-        self.assertEquals(['cmark', 'llvm', 'swift', 'swiftpm'], names)
+        self.assertEqual(['cmark', 'llvm', 'swift', 'swiftpm'], names)