Info-fontify-maximum-menu-size

Info-fontify-maximum-menu-size is a variable defined in `info.el'.
Its value is

400000

Documentation:
Maximum size of menu to fontify if `font-lock-mode' is non-nil.
Set to nil to disable node fontification; set to t for no limit.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 25.1 of Emacs.