Move what not to commit page to Package section (#5957)

Fixes #5690

Author: atsansone

src/_data/side-nav.yml

@@ -184,6 +184,8 @@
           permalink: /tools/pub/security-advisories
         - title: Versioning
           permalink: /tools/pub/versioning
+    - title: What not to commit
+      permalink: /guides/libraries/private-files
 
 - title: Development
   expanded: false
@@ -334,9 +336,6 @@
         permalink: /guides/testing
       - title: Debugging web apps
         permalink: /web/debugging
-  - title: What not to commit
-    permalink: /guides/libraries/private-files
-
 
 - divider
 - title: Resources