refactor(测试计划): 调整测试计划实际结果的字数限制

--story=1011022 --user=李玉号
调整测试计划实际结果的字数限制（将300调整为500）
https://www.tapd.cn/55049933/s/1325158

Closes #21156

test-track/frontend/src/business/plan/view/comonents/functional/FunctionalTestCaseEdit.vue

@@ -301,9 +301,9 @@ export default {
         let result = {};
         result.actualResult = this.testCase.steptResults[i].actualResult;
         result.executeResult = this.testCase.steptResults[i].executeResult;
-        if (result.actualResult && result.actualResult.length > 300) {
+        if (result.actualResult && result.actualResult.length > 500) {
           this.$warning(this.$t('test_track.plan_view.actual_result')
-            + this.$t('test_track.length_less_than') + '300');
+            + this.$t('test_track.length_less_than') + '500');
           return;
         }
         if (result.executeResult === 'Failure' && this.testCase.status === 'Pass') {