fix: pre/next's style of Tabs' vertical mode (#5784)

When tabPostition = 'left' | | 'right, slideButton should be on the up and down, but the actual in left and right

Signed-off-by: Min <dicklwm@163.com>

components/tabs/style/index.less

@@ -235,6 +235,7 @@
 
       .@{tab-prefix-cls}-nav-container {
         margin-bottom: 0;
+        padding: 32px 0;
       }
 
       .@{tab-prefix-cls}-nav-wrap {
@@ -254,6 +255,24 @@
       width: auto;
       margin-top: 0!important;
     }
+
+    .@{tab-prefix-cls}-tab-next {
+      width: 100%;
+      bottom: 0;
+      height: 32px;
+      &-icon:before {
+        content: "\e61d";
+      }
+    }
+
+    .@{tab-prefix-cls}-tab-prev {
+      top: 0;
+      width: 100%;
+      height: 32px;
+      &-icon:before {
+        content: "\e61e";
+      }
+    }
   }
 
   &-vertical&-left {