portico: Use relative links on recently merged pages.

We apparently forgot to do this conversion when importing them into
the codebase.

templates/zerver/for/communities.md

@@ -24,7 +24,7 @@ facilitating inclusion, and making efficient use of everyone’s time.
 <blockquote class="twitter-tweet"><p lang="en" dir="ltr">When we made the switch to <a href="https://twitter.com/zulip?ref_src=twsrc%5Etfw">@zulip</a> a few months ago for chat, never in my wildest dreams did I imagine it was going to become the beating heart of the community, and so quickly. It&#39;s a game changer. 🧑‍💻🗨️👩‍💻</p>&mdash; Dan Allen (@mojavelinux) <a href="https://twitter.com/mojavelinux/status/1409702273400201217?ref_src=twsrc%5Etfw">June 29, 2021</a></blockquote>
 &nbsp;
 
-If you haven’t read [Why Zulip](https://zulip.com/why-zulip), read
+If you haven’t read [Why Zulip](/why-zulip), read
 that first. The challenges with the Slack/Discord/IRC model discussed
 there are even more important for open communities:
 
@@ -89,7 +89,7 @@ Zulip’s topic-based threading model solves these problems:
   them to fully participate in the work of the community.
 - Community leaders can effectively participate in a Zulip community
   without being continuously online. Using Zulip’s [keyboard
-  shortcuts](https://zulip.com/help/keyboard-shortcuts), it’s
+  shortcuts](/help/keyboard-shortcuts), it’s
   extremely efficient to inspect every potentially relevant thread and
   reply wherever one’s feedback is useful, and replying hours after a
   question was asked is still a good experience for community
@@ -117,9 +117,9 @@ managing the community and spending most of their time integrating
 improvements into Zulip.
 
 Many communities that migrated from
-[Slack](https://zulip.com/help/import-from-slack),
+[Slack](/help/import-from-slack),
-[Mattermost](https://zulip.com/help/import-from-mattermost), or
+[Mattermost](/help/import-from-mattermost), or
-[Gitter](https://zulip.com/help/import-from-gitter) to Zulip tell us
+[Gitter](/help/import-from-gitter) to Zulip tell us
 that Zulip helped them manage and grow an inclusive, healthy
 community. We hope Zulip can help your community succeed too!
 

templates/zerver/for/ucsd-case-study.md

@@ -24,7 +24,7 @@ threaded model (which I find sorely lacking in other chat apps), and
 the TeX integration.”
 
 From Spring 2020 through Spring 2021, the [Zulip
-Standard](https://zulip.com/plans/) plan was free for all educators,
+Standard](/plans/) plan was free for all educators,
 as we did our part to help make the transition to online education a
 little easier. Having set up Zulip Cloud for his three graduate-level
 courses, Kiran felt confident in the communication platform, and was
@@ -56,21 +56,21 @@ the benefits of just a few of Zulip’s features:
 
 
 - **Discussing math**: “The
-  [**TeX**](https://zulip.com/help/format-your-message-using-markdown#latex)
+  [**TeX**](/help/format-your-message-using-markdown#latex)
   made it made it super easy to discuss material from the course using
   proper mathematical notation, and was one of the reasons I chose
   Zulip in the first place.”
 - **Quick pulse-checks**: “[**Emoji
-  reactions**](https://zulip.com/help/emoji-reactions) were a nice way
+  reactions**](/help/emoji-reactions) were a nice way
   to collect RSVPs for office hours or acknowledge typo corrections
   for my lecture notes.”
 - **Hiding answers**:
-  “[**Spoilers**](https://zulip.com/help/format-your-message-using-markdown#spoilers)
+  “[**Spoilers**](/help/format-your-message-using-markdown#spoilers)
   are a great way to answer questions about homework without depriving
   students of a chance to keep thinking about the problem on their
   own.”
 - **Scheduling**: “With [**local
-  times**](https://zulip.com/help/format-your-message-using-markdown#mention-a-time),
+  times**](/help/format-your-message-using-markdown#mention-a-time),
   I could announce office hours or outside lectures without having to
   worry about confusion for students in different time zones.”