help: Update content for include files in create-channels article.

Updates the content in `help/include/create-a-channel-instructions`
and `help/include/create-channels-intro` for the stream to channel
rename. Done in a separate commit from the previous so that the
rename of these files is tracked as such in the history.

help/include/create-a-channel-instructions.md

@@ -4,28 +4,28 @@
 
 {relative|gear|stream-settings}
 
-1. Click **Create stream** on the right, or click the **plus**
+1. Click **Create channel** on the right, or click the **plus**
    (<i class="fa fa-plus"></i>) icon in the upper right.
 
 1. Fill out the requested info, and click **Create** in the bottom right corner
-   of the create stream panel.
+   of the create channel panel.
 
 !!! warn ""
 
-    **Note**: You will only see the **Create stream** button if you have
+    **Note**: You will only see the **Create channel** button if you have
-    permission to create streams.
+    permission to create channels.
 
 {tab|mobile}
 
 {!mobile-all-streams-view.md!}
 
-1. Tap the **Create new stream** button at the top of the app.
+1. Tap the **Create new channel** button at the top of the app.
 
 1. Fill out the requested info, and tap **Create**.
 
 !!! warn ""
 
-    **Note**: You will only see the **Create new stream** button if you have
+    **Note**: You will only see the **Create new channel** button if you have
-    permission to create streams.
+    permission to create channels.
 
 {end_tabs}

help/include/create-channels-intro.md

@@ -1,13 +1,13 @@
-In Zulip, streams determine who gets a message. They are similar to
+In Zulip, channels determine who gets a message. They are similar to
 channels in IRC/Slack/Discord, chat rooms, and email lists.
 
-We recommend setting up some streams before inviting other users to
+We recommend setting up some channels before inviting other users to
 join Zulip, so that you can [automatically subscribe
 everyone](/help/set-default-streams-for-new-users) to the right set of
-streams.
+channels.
 
-If you later create additional streams, no worries! You can always add
+If you later create additional channels, no worries! You can always add
-a group of users or all the members of another stream to a new stream.
+a group of users or all the members of another channel to a new channel.
 
 !!! tip ""
-    Add clear descriptions to your streams, especially public streams.
+    Add clear descriptions to your channels, especially public channels.