fix: ghost button style (#31780)

* fix: Button ghost style broken when it is danger

* update snapshot

components/button/__tests__/__snapshots__/demo.test.ts.snap

@@ -325,6 +325,14 @@ exports[`renders ./components/button/demo/ghost.md correctly 1`] = `
       Dashed
     </span>
   </button>
+  <button
+    class="ant-btn ant-btn-primary ant-btn-background-ghost ant-btn-dangerous"
+    type="button"
+  >
+    <span>
+      Danger
+    </span>
+  </button>
 </div>
 `;
 

components/button/demo/ghost.md

@@ -25,6 +25,9 @@ ReactDOM.render(
     <Button type="dashed" ghost>
       Dashed
     </Button>
+    <Button type="primary" danger ghost>
+      Danger
+    </Button>
   </div>,
   mountNode,
 );

components/button/style/index.less

@@ -195,7 +195,7 @@
     margin-left: @margin-xs;
   }
 
-  &-background-ghost {
+  &&-background-ghost {
     color: @btn-default-ghost-color;
     border-color: @btn-default-ghost-border;
     &,