Update _config.yml

updated _config html generation execution to 'off' per standards

_config.yml

@@ -13,7 +13,7 @@ logo                        : _static/stsci_logo2.png  # A path to the book logo
 # Force re-execution of notebooks on each build.
 # See https://jupyterbook.org/content/execute.html
 execute:
-  execute_notebooks         : force   # Whether to execute notebooks at build time. Must be one of ("auto", "force", "cache", "off")
+  execute_notebooks         : off   # Whether to execute notebooks at build time. Must be one of ("auto", "force", "cache", "off")
   timeout                   : -1    # timeout in seconds, -1 removes timeout restrictions
   only_build_toc_files: true