Revert "gh-128639: Don't assume one thread in subinterpreter finalization (gh-128640)" (gh-134256)

This reverts commit 9859791f9e.

The original change broke the iOS and android buildbots, where the tests are run single-process.

Lib/test/test_interpreters/test_api.py

@@ -647,59 +647,6 @@ class TestInterpreterClose(TestBase):
                     self.interp_exists(interpid))
 
 
-    def test_remaining_threads(self):
-        r_interp, w_interp = self.pipe()
-
-        FINISHED = b'F'
-
-        # It's unlikely, but technically speaking, it's possible
-        # that the thread could've finished before interp.close() is
-        # reached, so this test might not properly exercise the case.
-        # However, it's quite unlikely and I'm too lazy to deal with it.
-        interp = interpreters.create()
-        interp.exec(f"""if True:
-            import os
-            import threading
-            import time
-
-            def task():
-                time.sleep(1)
-                os.write({w_interp}, {FINISHED!r})
-
-            threads = [threading.Thread(target=task) for _ in range(3)]
-            for t in threads:
-                t.start()
-            """)
-        interp.close()
-
-        self.assertEqual(os.read(r_interp, 1), FINISHED)
-
-    def test_remaining_daemon_threads(self):
-        interp = _interpreters.create(
-            types.SimpleNamespace(
-                use_main_obmalloc=False,
-                allow_fork=False,
-                allow_exec=False,
-                allow_threads=True,
-                allow_daemon_threads=True,
-                check_multi_interp_extensions=True,
-                gil='own',
-            )
-        )
-        _interpreters.exec(interp, f"""if True:
-            import threading
-            import time
-
-            def task():
-                time.sleep(100)
-
-            threads = [threading.Thread(target=task, daemon=True) for _ in range(3)]
-            for t in threads:
-                t.start()
-            """)
-        _interpreters.destroy(interp)
-
-
 class TestInterpreterPrepareMain(TestBase):
 
     def test_empty(self):
@@ -808,10 +755,7 @@ class TestInterpreterExec(TestBase):
                 spam.eggs()
 
             interp = interpreters.create()
-            try:
-                interp.exec(script)
-            finally:
-                interp.close()
+            interp.exec(script)
             """)
 
         stdout, stderr = self.assert_python_failure(scriptfile)
@@ -820,7 +764,7 @@ class TestInterpreterExec(TestBase):
         #      File "{interpreters.__file__}", line 179, in exec
         self.assertEqual(stderr, dedent(f"""\
             Traceback (most recent call last):
-              File "{scriptfile}", line 10, in <module>
+              File "{scriptfile}", line 9, in <module>
                 interp.exec(script)
                 ~~~~~~~~~~~^^^^^^^^
               {interpmod_line.strip()}