[FIX] website: remove misleading comment (gradient variables)

closes odoo/odoo#75276

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/website/static/src/scss/secondary_variables.scss

@@ -139,8 +139,7 @@ $-actual-user-color-palette: map-merge($-palette-default, o-map-omit($o-user-col
     // Each of those values were either a number for a color combination, a
     // string for a color name or a color. Now they should only be a number for
     // a color combination and the other value types for the color name/value
-    // are handled by another variable. That variable can also contain a string
-    // for a color gradient.
+    // are handled by another variable.
     'menu': 'menu-custom',
     'header-boxed': 'header-boxed-custom',
     'footer': 'footer-custom',