Remove unused style and classes

https://youtrack.weseek.co.jp/issue/GW-7910
- Remove unused scss file
- Adjust class of UncontrolledDropdown in BookmarkFolderMenu component
- Remove toggle button class (DropdownToggle already has color props)

packages/app/src/components/Bookmarks/BookmarkFolderMenu.module.scss

@@ -1,10 +0,0 @@
-.grw-bookmark-folder-dropdown :global {
-  .grw-bookmark-folder-menu {
-    .grw-bookmark-folder-menu-item {
-      svg,
-      .grw-bookmark-folder-menu-toggle-btn svg {
-        background-color: transparent;
-      }
-    }
-  }
-}

packages/app/src/components/Bookmarks/BookmarkFolderMenu.tsx

@@ -18,7 +18,6 @@ import FolderIcon from '../Icons/FolderIcon';
 import BookmarkFolderMenuItem from './BookmarkFolderMenuItem';
 import BookmarkFolderNameInput from './BookmarkFolderNameInput';
 
-import styles from './BookmarkFolderMenu.module.scss';
 
 type Props = {
   children?: React.ReactNode
@@ -128,7 +127,7 @@ const BookmarkFolderMenu = (props: Props): JSX.Element => {
   return (
     <UncontrolledDropdown
       direction={ isBookmarkFolderExists() ? 'up' : 'down' }
-      className={`grw-bookmark-folder-dropdown ${styles['grw-bookmark-folder-dropdown']}`}>
+      className='grw-bookmark-folder-dropdown'>
       {children}
       <DropdownMenu
         right

packages/app/src/components/Bookmarks/BookmarkFolderMenuItem.tsx

@@ -160,7 +160,6 @@ const BookmarkFolderMenuItem = (props: Props):JSX.Element => {
       </div>
       <DropdownToggle
         color="transparent"
-        className='grw-bookmark-folder-menu-toggle-btn '
         onClick={e => e.stopPropagation()}
         onMouseEnter={onMouseEnterHandler}
       >