fix(components): [cascader] fix large interval when multiple checkboxes (element-plus#9428)

* fix(theme-chalk): [cascader] fix large interval when multiple checkboxes

* fix(theme-chalk): separate style

Author: Chuck-Lau

packages/theme-chalk/src/cascader-panel.scss

@@ -124,6 +124,10 @@
     text-overflow: ellipsis;
   }
 
+  > .#{$namespace}-checkbox {
+    margin-right: 0;
+  }
+
   > .#{$namespace}-radio {
     margin-right: 0;