Built-in documentation text width in Lighthouse book (#5394)

* Adjust width

* Commit changes

* Trigger Build

book/src/help_general.md

@@ -104,4 +104,5 @@ SUBCOMMANDS:
                          blocks and attestations). [aliases: v, vc, validator]
     validator_manager    Utilities for managing a Lighthouse validator client via the HTTP API. [aliases: vm,
                          validator-manager, validator_manager]
-```
+```
+<style> .content main {max-width:88%;} </style>