fix(gui): 调整多个UI预制件的布局参数

1. 修正hero.prefab中多个节点的y轴位置与布局边界值
2. 调整sibox.prefab的节点位置、内容尺寸与字体大小
3. 移除sibox.prefab中冗余的bg_node引用

assets/resources/gui/element/heros.prefab

@@ -1394,7 +1394,7 @@
     "_lpos": {
       "__type__": "cc.Vec3",
       "x": 0,
-      "y": -2.252,
+      "y": 74.047,
       "z": 0
     },
     "_lrot": {
@@ -2226,7 +2226,7 @@
     "_lpos": {
       "__type__": "cc.Vec3",
       "x": 0,
-      "y": -132.818,
+      "y": -108.162,
       "z": 0
     },
     "_lrot": {
@@ -10985,7 +10985,7 @@
     "_lpos": {
       "__type__": "cc.Vec3",
       "x": 0,
-      "y": -218.836,
+      "y": -199.317,
       "z": 0
     },
     "_lrot": {
@@ -11489,8 +11489,8 @@
     "_target": null,
     "_left": 30,
     "_right": 30,
-    "_top": 553.836,
-    "_bottom": 116.16400000000002,
+    "_top": 534.317,
+    "_bottom": 135.68299999999996,
     "_horizontalCenter": 0,
     "_verticalCenter": 0,
     "_isAbsLeft": true,