gh-155648: In IDLE tests, call unittest.main without exit arg

In idlelib.idle_test, test_xyz.py files should end with
```
if __name__ == '__main__':
    unittest.main(verbosity=2, exit=0)
```
5 files add the possibly confusing `exit=2` ("why?"),
which is equivalent to the default `exit=True`.

4 files add `exit=False`.  This is also nonsensical when there
is nothing more to run; main will immediately exit anyway.
When running the test from an IDLE editor, this argument
has no visible effect.  However, A Claude-based
bug finder claims that in other circumstances (such as a program running
the test in a shell), the good test may falsely fail. Even if this is
not true, it can only confuse a reader.

Author: terryjreedy

Lib/idlelib/idle_test/test_delegator.py

@@ -41,4 +41,4 @@ def test_mydel(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=2)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_format.py

@@ -665,4 +665,4 @@ def test_rstrip_end(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=2)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_history.py

@@ -169,4 +169,4 @@ def test_history_prev_next(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=2)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_pathbrowser.py

@@ -83,4 +83,4 @@ def test_PathBrowserTreeItem(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=False)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_query.py

@@ -448,4 +448,4 @@ def test_click_args(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=False)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_search.py

@@ -77,4 +77,4 @@ def test_find_selection(self):
         text.delete('2.0', 'end')
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=2)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_searchbase.py

@@ -157,4 +157,4 @@ def test_create_command_buttons(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=2)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_text.py

@@ -233,4 +233,4 @@ def setUp(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=False)
+    unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_undo.py

@@ -132,4 +132,4 @@ def test_addcmd(self):
 
 
 if __name__ == '__main__':
-    unittest.main(verbosity=2, exit=False)
+    unittest.main(verbosity=2)