node tests: Use mock_template in i18n.
node tests: Use mock_template in i18n.

This appears to be a silly case of using mock_template,
since the tests directly "require" the template, but
we are using it here to set up a generalization.

13 choose 1 is obviously 13, but it's also 13! divided
by the product of 12! and 1!.

The cruftiest part of this change gets fixed by the
subsequent commit (no need to call mock_template at
the top level).

rht/zulip,rht/zulip,hackerkid/zulip,hackerkid/zulip,andersk/zulip,punchagan/zulip,andersk/zulip,zulip/zulip,andersk/zulip,rht/zulip,andersk/zulip,andersk/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,kou/zulip,rht/zulip,punchagan/zulip,zulip/zulip,zulip/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,punchagan/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,punchagan/zulip,zulip/zulip,punchagan/zulip,hackerkid/zulip,rht/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,punchagan/zulip,eeshangarg/zulip,zulip/zulip,kou/zulip