chore: remove unnecessary responsive layout

The CSS in the base template was updated to include this directive in #7695
and released in sphinx v3.1.0.

The original implementation was in python#46, prior to the basic theme
including it, and now we have the same meta tag duplicated.

Remove the block, and reduce the duplication.

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

python_docs_theme/layout.html

@@ -82,11 +82,6 @@ <h3>{{ _('Navigation') }}</h3>
     {{ super() }}
 {%- endblock -%}
 
-{%- block css -%}
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    {{ super() }}
-{%- endblock -%}
-
 {%- block body_tag %}
 {{ super() }}
 {%- if builder != 'htmlhelp' %}