computed_settings: Remove deprecated Jinja2 autoescape extension.
computed_settings: Remove deprecated Jinja2 autoescape extension.

It’s built in to Jinja2 as of 2.9.  Fixes “DeprecationWarning: The
'autoescape' extension is deprecated and will be removed in Jinja
3.1. This is built in now.”

Signed-off-by: Anders Kaseorg <dfdb7392591db597bc41cf266a9c3bc12a2706e5@zulip.com>

eeshangarg/zulip,kou/zulip,rht/zulip,zulip/zulip,zulip/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,andersk/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,kou/zulip,andersk/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,kou/zulip,kou/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,zulip/zulip,rht/zulip,andersk/zulip,andersk/zulip,kou/zulip,andersk/zulip,zulip/zulip