Update to PreTeXt project source.

Author: fragandi

source/main.ptx

@@ -21,7 +21,7 @@
     <xi:include href="ch-first-repo.ptx"/>
     <xi:include href="ch-coding.ptx"/>
     <xi:include href="ch-website.ptx"/>
-    <xi:include href="ch-copilot.ptx"/>
+    <!-- <xi:include href="ch-copilot.ptx"/> -->
     <xi:include href="ch-collaboration.ptx"/>
     <xi:include href="ch-jupyter.ptx"/>
     <xi:include href="ch-projects.ptx"/>