fix(contextmenu): change contextMenu style (#501)

Author: LuckyFBB

src/contextMenu/style.scss

@@ -1,19 +1,4 @@
 .dtc-contextMenu-menu {
-    padding: 0;
-    background: #FFF;
-    box-shadow: 0 1px 6px rgba(0, 0, 0, 0.2);
-    border-radius: 2px;
     min-width: 90px;
     max-width: 160px;
-    .ant-dropdown-menu-item {
-        color: rgba(0, 0, 0, 0.65);
-        font-size: 12px;
-        font-weight: normal;
-        white-space: nowrap;
-        text-decoration: none;
-        line-height: inherit;
-        &:hover {
-            background: #EEF6FE;
-        }
-    }
 }