Fix border of active tab in L/R sidebar (#5039)

* Fix display of tabs in sidebar.

* Make it pretty.

packages/application/style/sidepanel.css

@@ -66,6 +66,16 @@
   overflow: visible;
 }
 
+.jp-SideBar .p-TabBar-tab.p-mod-current {
+  min-height: calc(
+    var(--jp-private-sidebar-tab-width) + var(--jp-border-width)
+  );
+  max-height: calc(
+    var(--jp-private-sidebar-tab-width) + var(--jp-border-width)
+  );
+  transform: translateY(var(--jp-border-width));
+}
+
 .jp-SideBar .p-TabBar-tab:not(.p-mod-current) {
   background: var(--jp-layout-color2);
 }

packages/filebrowser/style/index.css

@@ -31,6 +31,7 @@
   border-bottom: none;
   height: auto;
   margin: var(--jp-toolbar-header-margin);
+  box-shadow: none;
 }
 
 .jp-BreadCrumbs {