Remove obsolete usage of gl.lazyLoader.loadCheck

In [!21565][0] we removed the loadCheck function from the LazyLoader for
images. The function seemed to be obsolete before anyhow, because we
make use of the MutationObserver in order to detect elements added /
removed from the DOM.

[0]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21565

app/assets/javascripts/main.js

@@ -202,7 +202,6 @@ document.addEventListener('DOMContentLoaded', () => {
   $('.navbar-toggler').on('click', () => {
     $('.header-content').toggleClass('menu-expanded');
-    gl.lazyLoader.loadCheck();
   });
   // Show/hide comments on diff

app/assets/javascripts/right_sidebar.js

@@ -57,8 +57,6 @@ Sidebar.prototype.sidebarToggleClicked = function (e, triggered) {
     $allGutterToggleIcons.removeClass('fa-angle-double-left').addClass('fa-angle-double-right');
     $('aside.right-sidebar').removeClass('right-sidebar-collapsed').addClass('right-sidebar-expanded');
     $('.layout-page').removeClass('right-sidebar-collapsed').addClass('right-sidebar-expanded');
-
-    if (gl.lazyLoader) gl.lazyLoader.loadCheck();
   }
   $this.attr('data-original-title', tooltipLabel);

changelogs/unreleased/52532-unable-to-toggle-issuable-sidebar-out-of-collapsed-state.yml

+---
+title: Allow Issue and Merge Request sidebar to be toggled from collapsed state
+merge_request: 22353
+author:
+type: fixed

spec/javascripts/right_sidebar_spec.js

@@ -94,33 +94,5 @@ import Sidebar from '~/right_sidebar';
         });
       });
     });
-
-    describe('sidebarToggleClicked', () => {
-      const event = jasmine.createSpyObj('event', ['preventDefault']);
-
-      beforeEach(() => {
-        spyOn($.fn, 'hasClass').and.returnValue(false);
-      });
-
-      afterEach(() => {
-        gl.lazyLoader = undefined;
-      });
-
-      it('calls loadCheck if lazyLoader is set', () => {
-        gl.lazyLoader = jasmine.createSpyObj('lazyLoader', ['loadCheck']);
-
-        Sidebar.prototype.sidebarToggleClicked(event);
-
-        expect(gl.lazyLoader.loadCheck).toHaveBeenCalled();
-      });
-
-      it('does not throw if lazyLoader is not defined', () => {
-        gl.lazyLoader = undefined;
-
-        const toggle = Sidebar.prototype.sidebarToggleClicked.bind(null, event);
-
-        expect(toggle).not.toThrow();
-      });
-    });
   });
 }).call(window);