cleanup: Remove yadm-theme guides

I've removed that helepr a while back

Author: ixti

README.adoc

@@ -6,27 +6,6 @@
 * (optional) vivid (https://github.com/sharkdp/vivid[homepage] | https://github.com/gentoo/guru/tree/master/app-shells/vivid[ebuild])
 * (optional) starship (https://starship.rs/[homepage] | https://packages.gentoo.org/packages/app-shells/starship[ebuild])
 
-== Theming
-
-By default, I'm using gruvbox, but sometimes I love to experiment with themes :D
-To make it easier, I'm using yadm alternatives using `theme:{name}` class, e.g.:
-
-[source,bash]
-----
-# Set theme to catppuccin_frappe
-yadm config --add local.class theme:catppuccin_frappe
-
-# Switch back to default theme
-yadm config --unset-all local.class 'theme:*'
-----
-
-There's also a helper for that:
-
-[source,bash]
-----
-yadm-theme catppuccin_frappe
-----
-
 == Install
 
 [source,bash]