Fixed #27759 -- Prevented forms attrs.html template from rendering False attrs.

Regression in b52c7300.

django/forms/jinja2/django/forms/widgets/attrs.html

-{% for name, value in widget.attrs.items() %} {{ name }}{% if not value is sameas True %}="{{ value }}"{% endif %}{% endfor %}
+{% for name, value in widget.attrs.items() %}{% if value is not sameas False %} {{ name }}{% if not value is sameas True %}="{{ value }}"{% endif %}{% endif %}{% endfor %}

django/forms/templates/django/forms/widgets/attrs.html

-{% for name, value in widget.attrs.items %} {{ name }}{% if not value is True %}="{{ value }}"{% endif %}{% endfor %}
+{% for name, value in widget.attrs.items %}{% if value is not False %} {{ name }}{% if not value is True %}="{{ value }}"{% endif %}{% endif %}{% endfor %}
\ No newline at end of file

tests/forms_tests/widget_tests/test_widget.py

@@ -13,3 +13,7 @@ class WidgetTests(WidgetTest):
 
     def test_no_trailing_newline_in_attrs(self):
         self.check_html(Input(), 'name', 'value', strict=True, html='<input type="None" name="name" value="value" />')
+
+    def test_attr_false_not_rendered(self):
+        html = '<input type="None" name="name" value="value" />'
+        self.check_html(Input(), 'name', 'value', html=html, attrs={'readonly': False})