remove duplicated line

(cherry picked from commit 5d04e44)

Author: saschaszott

src/styles/_bootstrap_variables_mapping.scss

@@ -220,7 +220,6 @@
   --bs-table-dark-hover-color: #{$table-dark-hover-color};
   --bs-table-dark-hover-bg: #{$table-dark-hover-bg};
   --bs-table-dark-border-color: #{$table-dark-border-color};
-  --bs-table-dark-color: #{$table-dark-color};
   --bs-table-striped-order: #{$table-striped-order};
   --bs-table-caption-color: #{$table-caption-color};
   --bs-table-bg-level: #{$table-bg-level};