fix(highlight-indent-guides): for terminal users

[Sleepful]

(when (display-graphic-p)) is always nil for terminal emacs

I tested it on my machine, I run emacs as daemon in kitty terminal.

Before this change:

• start emacs
• highlight-indent-guides-mode is on (through :ui indent-guides)
• however there are no indent lines visible
• changing doom themes manually with load-theme allows indent guides to be shown. Manually calling highlight-indent-guides-auto-set-faces has the same effect.

After change:

• start emacs
• indent-guides are displayed on files without any issue

---

• I searched the issue tracker and this hasn't been PRed before.
• My commits conform to the git conventions.
• My changes are visual; I've included before and after screenshots.
• I am blindly checking these off. 🤣

[hlissner]

As of 9d4689d this should be resolved. Thanks for your help! Let me know if it doesn't fix the issue.