Revert "fix: disabled node can be checked"

src/components/tree/tree.vue

@@ -174,11 +174,7 @@
                 if (this.checkStrictly) return;
 
                 for (let key in changes) {
-                    if (key === 'checked' && node.disabled) {
-                        this.$set(node, key, node.checked);
-                    } else {
-                        this.$set(node, key, changes[key]);
-                    }
+                    this.$set(node, key, changes[key]);
                 }
                 if (node[this.childrenKey]) {
                     node[this.childrenKey].forEach(child => {