corporate: Rename stream->channel in TUM case study.

templates/corporate/case-studies/tum-case-study.md

@@ -35,7 +35,7 @@ Tobias evaluated Zulip by [visiting the Zulip development
 community](/try-zulip/) to see it in action. “It takes a bit of
 time to get used to, but Zulip has the best user experience of all the
 chat apps I’ve tried,” Tobias says. “With the discussion organized by
-topic within each stream, Zulip is the only app that makes hundreds of
+topic within each channel, Zulip is the only app that makes hundreds of
 conversations manageable.”
 
 Despite initially asking to use Slack, students came to love Zulip’s

templates/corporate/for/education.html

@@ -67,7 +67,7 @@
                 </ul>
                 <div class="quote">
                     <blockquote>
-                        Zulip has the best user experience of all the chat apps I’ve tried. With the discussion organized by topic within each stream, Zulip is the only app that makes hundreds of conversations manageable.
+                        Zulip has the best user experience of all the chat apps I’ve tried. With the discussion organized by topic within each channel, Zulip is the only app that makes hundreds of conversations manageable.
                     </blockquote>
                     <div class="author">
                         &mdash; <a href="https://ciip.in.tum.de/people/lasser.html">Tobias Lasser</a>, lecturer at the Technical University of Munich Department of Informatics

templates/corporate/history.md

@@ -196,7 +196,7 @@ Zulip Cloud increased an incredible 40x in the month after Slack’s
   dedicated [Zulip for Education](/for/education/) offering.
 
 > “Zulip has the best user experience of all the chat apps I’ve tried. With the
-> discussion organized by topic within each stream, Zulip is the only app that
+> discussion organized by topic within each channel, Zulip is the only app that
 > makes hundreds of conversations manageable.”
 >
 > — [Tobias Lasser](https://ciip.in.tum.de/people/lasser.html), lecturer at the