Explicitly export Select and WebDriverWait from selenium.webdriver.support.ui (#13491)

Without this, `mypy` in strict mode gives:

```
Module "selenium.webdriver.support.ui" does not explicitly export attribute "Select"  [attr-defined]
```

when following the documentation at https://selenium-python.readthedocs.io/navigating.html#filling-in-forms.

Co-authored-by: Diego Molina <[email protected]>

Author: adamtheturtle

py/selenium/webdriver/support/ui.py

@@ -15,5 +15,7 @@
 # specific language governing permissions and limitations
 # under the License.
 
-from .select import Select  # noqa
-from .wait import WebDriverWait  # noqa
+from .select import Select
+from .wait import WebDriverWait
+
+__all__ = ["Select", "WebDriverWait"]