Collapse region is always hidden rule is problematic

Problem/Motivation

In bs_bootstrap/sass/layout/partials/_header.scss there is a next CSS rule

  // When navbar collapse responsive break is the largest breakpoint then we
  // need to modify displays of navbar collapse region and toggler.
  @if breakpoint-max($navbar-collapse-responsive-break) == null {
    // Collapse region is always hidden except when it is in screen.
    .region-navbar:not(.in) {
      display: none !important;
    }

This makes problem with some specific offcanvas navigation configurations and cases. Also it does not make sense because we have offcanvas class on that element that is doing exactly this - hiding this element until `in` class in not attached.

Let's try to remove this for now.