help_docs: Update `rename-a-stream` help doc.

Uses new `select-stream-view-general.md` for instructions.

Also, updates text for locating the button/icon and uses
the `save-changes.md` to correct the final instruction/step.

templates/zerver/help/rename-a-stream.md

@@ -8,9 +8,11 @@
 
 1. Select a stream.
 
-1. On the right, click the **pencil** (<i class="fa fa-pencil"></i>)
-   next to the stream name. Enter a new name.
+{!select-stream-view-general.md!}
 
-1. Click the **checkmark** to save.
+1. Click the **pencil** (<i class="fa fa-pencil"></i>)
+   to the right of the stream name. Enter a new name.
+
+{!save-changes.md!}
 
 {end_tabs}