[BUG] outdated _bootstrap-variables.scss breaks pagination buttons

[Kneemund]

The currently used _bootstrap-variables.scss file is outdated compared to the current release of bootstrap.

Notably, the following line:

$pagination-margin-start: calc(#{$pagination-border-width} * -1);

was changed to:

$pagination-margin-start: calc(-1 * #{$pagination-border-width}); 

This causes a condition inside bootstrap's pagination classes to fail, and in turn makes all pagination buttons have a border radius on all sides (even though they should be a connected group).

Environment:

• AdminLTE Version: 4.0.0-rc6