[4.2.x] Refs #30220 -- Bumped required version of Selenium to 3.8.0.

Follow up to 8d010f3986.
Backport of 06881341d4 from main

docs/internals/contributing/writing-code/unit-tests.txt

@@ -296,7 +296,7 @@ dependencies:
   <https://memcached.org/>`_
 * `gettext <https://www.gnu.org/software/gettext/manual/gettext.html>`_
   (:ref:`gettext_on_windows`)
-* :pypi:`selenium`
+* :pypi:`selenium` 3.8.0+
 * :pypi:`sqlparse` 0.3.1+ (required)
 * :pypi:`tblib` 1.5.0+
 

docs/topics/testing/tools.txt

@@ -1035,7 +1035,7 @@ First of all, you need to install the :pypi:`selenium` package:
 
 .. console::
 
-    $ python -m pip install selenium
+    $ python -m pip install "selenium >= 3.8.0"
 
 Then, add a ``LiveServerTestCase``-based test to your app's tests module
 (for example: ``myapp/tests.py``). For this example, we'll assume you're using

tests/requirements/py3.txt

@@ -16,7 +16,7 @@ pytz
 pywatchman; sys.platform != 'win32'
 PyYAML
 redis >= 3.4.0
-selenium
+selenium >= 3.8.0
 sqlparse >= 0.3.1
 tblib >= 1.5.0
 tzdata