fix(components): [tree] revert inherits the label class (element-plus#10812)

* revert slot inherit style
* Adjust the size style attribute to tree

Author: chenxch

packages/components/tree/src/tree-node-content.vue

@@ -24,11 +24,9 @@ export default defineComponent({
       const { data, store } = node
       return props.renderContent
         ? props.renderContent(h, { _self: nodeInstance, node, data, store })
-        : h('span', { class: ns.be('node', 'label') }, [
-            tree.ctx.slots.default
-              ? tree.ctx.slots.default({ node, data })
-              : node.label,
-          ])
+        : tree.ctx.slots.default
+        ? tree.ctx.slots.default({ node, data })
+        : h('span', { class: ns.be('node', 'label') }, [node.label])
     }
   },
 })

packages/theme-chalk/src/tree.scss

@@ -12,6 +12,7 @@
   cursor: default;
   background: getCssVar('fill-color', 'blank');
   color: getCssVar('tree-text-color');
+  font-size: getCssVar('font-size', 'base');
 
   @include e(empty-block) {
     position: relative;
@@ -107,10 +108,6 @@
     }
   }
 
-  @include e(label) {
-    font-size: getCssVar('font-size', 'base');
-  }
-
   @include e(loading-icon) {
     margin-right: 8px;
     font-size: getCssVar('font-size', 'base');