[5.1.x] Fixed #34886 -- Modified sample use of lazy in delayed translations.

Modified example to use python standard library function
to lower the case of the string.

Backport of 136a5f9409 from main.

docs/topics/i18n/translation.txt

@@ -515,14 +515,18 @@ pass the translatable string as argument to another function, you can wrap
 this function inside a lazy call yourself. For example::
 
     from django.utils.functional import lazy
-    from django.utils.safestring import mark_safe
     from django.utils.translation import gettext_lazy as _
 
-    mark_safe_lazy = lazy(mark_safe, str)
+
+    def to_lower(string):
+        return string.lower()
+
+
+    to_lower_lazy = lazy(to_lower, str)
 
 And then later::
 
-    lazy_string = mark_safe_lazy(_("<p>My <strong>string!</strong></p>"))
+    lazy_string = to_lower_lazy(_("My STRING!"))
 
 Localized names of languages
 ----------------------------