refactor(nix): remove background image HSB adjustments

- Deleted `window_background_image_hsb` configuration for WezTerm.
- Simplifies the terminal setup by removing unnecessary brightness, hue, and saturation settings.
- Retains the custom background image for consistent aesthetics.

homes/x86_64-linux/harald@amd/default.nix

@@ -80,11 +80,6 @@
     config.enable_kitty_keyboard = true
     config.enable_scroll_bar = true
     config.window_background_image = '${./terminal-background.png}'
-    config.window_background_image_hsb = {
-      brightness = 0.5,
-      hue = 1.0,
-      saturation = 1.0,
-    }
 
     config.term = 'wezterm'