flavours: Fix zathura colorscheme file naming

In preparation for at some point leaving flavours in favour of tinty
(since flavours is not maintained anymore), started preparing a rough
translation of the config file for the new program. One of the things I
changed (to make more semantic sense) is the zathura colorscheme file
name.

desktop/.config/flavours/config.toml

@@ -53,7 +53,7 @@ rewrite = true
 
 [[items]]
 template = "zathura"
-file = "~/.local/state/zathura/zathurarc"
+file = "~/.local/state/zathura/colors.config"
 rewrite = true
 
 [[items]]

writing/.config/zathura/zathurarc

@@ -1,6 +1,6 @@
 # overwritten by below colors
 include colorscheme
-include /home/marty/.local/state/zathura/zathurarc
+include /home/marty/.local/state/zathura/colors.config
 
 set recolor                     "true"
 set selection-clipboard         "clipboard"