docs(notebooks): correct help text — OAuth2 is supported

The AUTHENTICATION block claimed OAuth2 is not supported, but the
notebooks_read / notebooks_write scopes work fine (see acp.rs, which
describes this accurately). Update the help to match reality and the
phrasing used by other commands in main.rs.

Closes #406

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: platinummonkey

src/main.rs

@@ -1889,8 +1889,8 @@ enum Commands {
     ///   pup notebooks delete 12345
     ///
     /// AUTHENTICATION:
-    ///   Requires API key authentication (DD_API_KEY + DD_APP_KEY).
-    ///   OAuth2 is not supported for this endpoint.
+    ///   Requires OAuth2 (via 'pup auth login') with notebooks_read/notebooks_write
+    ///   scopes, or API key authentication (DD_API_KEY + DD_APP_KEY).
     #[command(verbatim_doc_comment)]
     Notebooks {
         #[command(subcommand)]