[style] unify Vue widget/slot label colors (#6149)

## Summary

Change labels on all widgets and slots to the same value which matches
design spec.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6149-style-unify-Vue-widget-slot-label-colors-2916d73d3650810a98f3ee75e0b22da0)
by [Unito](https://www.unito.io)

---------

Co-authored-by: DrJKL <DrJKL0424@gmail.com>

src/renderer/extensions/vueNodes/widgets/components/WidgetFileUpload.vue

@@ -10,7 +10,7 @@
     <div class="mb-2 flex items-center justify-between gap-4 px-2">
       <label
         v-if="widget.name"
-        class="min-w-[4em] truncate text-xs opacity-80"
+        class="text-secondary min-w-[4em] truncate text-xs"
         >{{ widget.name }}</label
       >
       <!-- Group select and folder button together on the right -->
@@ -81,7 +81,7 @@
     <div class="mb-2 flex items-center justify-between gap-4 px-2">
       <label
         v-if="widget.name"
-        class="min-w-[4em] truncate text-xs opacity-80"
+        class="text-secondary min-w-[4em] truncate text-xs"
         >{{ widget.name }}</label
       >
       <!-- Group select and folder button together on the right -->