docs: merge error related pages

.changeset/wet-camels-laugh.md

@@ -0,0 +1,5 @@
+---
+"@fuel-ts/errors": patch
+---
+
+docs: merge error related pages

apps/docs/.vitepress/config.ts

@@ -512,13 +512,8 @@ export default defineConfig({
           {
             text: 'Errors',
             link: '/guide/errors/',
-            collapsed: true,
-            items: [
-              {
-                text: 'Error Codes',
-                link: '/guide/errors/error-codes',
-              },
-            ],
+            collapsed: false,
+            items: [],
           },
           apiLinks,
         ],