changed table-dark border-color

build/scss/_bootstrap-variables.scss

@@ -314,7 +314,7 @@ $table-head-color:            $gray-700 !default;
 $table-dark-bg:               $gray-900 !default;
 $table-dark-accent-bg:        rgba($white, .05) !default;
 $table-dark-hover-bg:         rgba($white, .075) !default;
-$table-dark-border-color:     lighten($gray-900, 7.5%) !default;
+$table-dark-border-color:     lighten($gray-900, 10%) !default;
 $table-dark-color:            $body-bg !default;