Hide scrollbar of sidebar

.changeset/lovely-panthers-peel.md

@@ -0,0 +1,8 @@
+---
+'@backstage/core': minor
+---
+
+Closes #3556
+The scrollbar of collapsed sidebar is now hidden wihtout full screen.
+
+![image](https://user-images.githubusercontent.com/46953622/105390193-0bfd0080-5c19-11eb-8e86-2161bbe6e8d9.png)

packages/core/src/layout/Sidebar/Bar.tsx

@@ -39,6 +39,8 @@ const useStyles = makeStyles<BackstageTheme>(theme => ({
     padding: 0,
     background: theme.palette.navigation.background,
     overflowX: 'hidden',
+    msOverflowStyle: 'none',
+    scrollbarWidth: 'none',
     width: sidebarConfig.drawerWidthClosed,
     transition: theme.transitions.create('width', {
       easing: theme.transitions.easing.sharp,
@@ -47,6 +49,9 @@ const useStyles = makeStyles<BackstageTheme>(theme => ({
     '& > *': {
       flexShrink: 0,
     },
+    '&::-webkit-scrollbar': {
+      display: 'none',
+    },
   },
   drawerOpen: {
     width: sidebarConfig.drawerWidthOpen,