Convert rendered string into SafeString

b/c the ability to return a str, rather than a SafeString has been
removed which breaks SimpleMDE rendering b/c the text gets escaped and
not rendered by the browser.

See: https://docs.djangoproject.com/en/5.0/releases/5.0/

tcms/core/widgets.py

@@ -1,11 +1,12 @@
-#   Copyright (c) 2018,2021 Kiwi TCMS project. All rights reserved.
+#   Copyright (c) 2018-2024 Kiwi TCMS project. All rights reserved.
 #   Author: Alexander Todorov <[email protected]>
 
 """
 Custom widgets for Django
 """
 from django import forms
 from django.utils.dateparse import parse_duration
+from django.utils.safestring import SafeString
 
 
 class SimpleMDE(forms.Textarea):
@@ -24,9 +25,11 @@ def render(self, name, value, attrs=None, renderer=None):
             }
         )
         rendered_string = super().render(name, value, attrs, renderer)
-        rendered_string += f"""
+        rendered_string += SafeString(
+            f"""
 <input id="{self.file_upload_id}" type="file" style="display: none">
 """
+        )
         return rendered_string
 
     class Media: