docs(list): fix missing slash that prevents sassdoc from building the correct documentation

Closes #5759

Signed-off-by: MPopov <desig9stein@gmail.com>

Author: MPopov

projects/igniteui-angular/src/lib/core/styles/components/list/_list-theme.scss

@@ -15,7 +15,7 @@
 /// @param {Color} $item-background [null] - The list item background color.
 /// @param {Color} $item-background-hover [null] - The list item hover background color.
 /// @param {Color} $item-background-active [null] - The active list item background color.
-//
+///
 /// @param {Color} $item-text-color [null] - The list item text color.
 /// @param {Color} $item-text-color-hover [null] - The list item hover text color.
 /// @param {Color} $item-text-color-active [null] - The active list item text color.