Add note on the intention of the test

Author: facelessuser

tests/test_syntax/extensions/test_md_in_html.py

@@ -1519,6 +1519,9 @@ def test_md1_code_cdata(self):
 
     def test_trailing_content_after_tag_in_md_block(self):
 
+        # It should be noted that this is not the way `md_in_html` is intended to be used.
+        # What we are specifically testing is an edge case where content was previously lost.
+        # Lost content should not happen.
         self.assertMarkdownRenders(
             self.dedent(
                 """