[3.10] bpo-25130: Add calls of gc.collect() in tests to support PyPy (GH-28005) (GH-28027)

(cherry picked from commit 2a8127cafe1d196f858a3ecabf5f1df3eebf9a12)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 12af22f..6e4772d 100755
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -870,6 +870,7 @@ def test_weakref(self):
             p = proxy(s)
             self.assertEqual(p.fileno(), s.fileno())
         s = None
+        support.gc_collect()  # For PyPy or other GCs.
         try:
             p.fileno()
         except ReferenceError: