Update flag summaries in authoring bundle documentation

Clarified descriptions for command flags in documentation.

Author: jshackell-sfdc

messages/agent.generate.authoring-bundle.md

@@ -16,15 +16,15 @@ This command requires an org because it uses it to access an LLM for generating
 
 # flags.spec.summary
 
-Path to the agent spec YAML file; if not specified, the command provides a list that you can choose from.
+Path to the agent spec YAML file.
 
 # flags.output-dir.summary
 
 Directory where the authoring bundle files are generated.
 
 # flags.name.summary
 
-Name (label) of the authoring bundle; if not specified, you're prompted for the name.
+Name (label) of the authoring bundle.
 
 # flags.api-name.summary