Update tests for URL handling in safe mode

In version 2.5.4, markdown2 has added better handling for URLs
containing a "+" sign (trentm/python-markdown2#623)

Update our tests accordingly.

Author: Maari Tamm

requirements/base.txt

@@ -6,3 +6,4 @@ edx-i18n-tools<1.6
 Mako<=1.3.10
 bleach<=6.2.0
 django<=4.3
+markdown2>=2.5.4

tests/test_basics.py

@@ -185,9 +185,8 @@ def test_render_url_safe_mode_replace(self):
         with patch('markdown_xblock.html.get_xblock_settings') as get_settings_mock:
             get_settings_mock.return_value = settings
             fragment = block.student_view()
-            # in replace mode, "+" in URLs turns into whitespace
             self.assertIn(
-                '<a href="https://test.com/courses/course-v1:Org Class Version/about">test1</a>',
+                '<a href="https://test.com/courses/course-v1:Org+Class+Version/about">test1</a>',
                 fragment.content
             )
             self.assertIn(
@@ -210,9 +209,8 @@ def test_render_url_safe_mode_escape(self):
         with patch('markdown_xblock.html.get_xblock_settings') as get_settings_mock:
             get_settings_mock.return_value = settings
             fragment = block.student_view()
-            # in escape mode, "+" in URLs turns into whitespace
             self.assertIn(
-                '<a href="https://test.com/courses/course-v1:Org Class Version/about">test1</a>',
+                '<a href="https://test.com/courses/course-v1:Org+Class+Version/about">test1</a>',
                 fragment.content
             )
             self.assertIn(