test: fix Vitest segmentation fault (#13415)

packages/vant/src/index-bar/test/__snapshots__/demo.spec.ts.snap

@@ -204,7 +204,7 @@ exports[`should render demo and match snapshot 1`] = `
             Y
           </span>
           <span
-            class="van-index-bar__index van-index-bar__index--active"
+            class="van-index-bar__index"
             data-index="Z"
           >
             Z
@@ -911,8 +911,8 @@ exports[`should render demo and match snapshot 1`] = `
           </div>
         </div>
         <div>
-          <div style="height: 0px;">
-            <div class="van-index-anchor van-index-anchor--sticky van-hairline--bottom">
+          <div>
+            <div class="van-index-anchor">
               Z
             </div>
           </div>

packages/vant/vitest.config.ts

@@ -1,9 +1,6 @@
 import { defineConfig } from 'vitest/config';
 import vitePluginVue from '@vitejs/plugin-vue';
 import vitePluginJsx from '@vitejs/plugin-vue-jsx';
-import { cpus } from 'os';
-
-const cpuNum = Math.max(cpus().length - 1, 1);
 
 export default defineConfig({
   test: {
@@ -20,13 +17,6 @@ export default defineConfig({
       reporter: ['lcov', 'text-summary'],
       reportsDirectory: './test/coverage',
     },
-    pool: 'vmThreads',
-    poolOptions: {
-      vmThreads: {
-        // limit the memory to avoid OOM
-        memoryLimit: Math.min(1 / (cpuNum * 2), 0.1),
-      },
-    },
     environment: 'jsdom',
     include: ['src/**/*.spec.[jt]s?(x)'],
     restoreMocks: true,