fix(测试跟踪): 功能用例回收站彻底删除提示问题

--bug=1040119 --user=宋昌昌 【测试跟踪】github#30567，功能用例回收站彻底删除用例，选择了全选所有页彻底删除所有用例，删除提示不对 https://www.tapd.cn/55049933/s/1585047

test-track/frontend/src/business/case/components/TestCaseList.vue

@@ -982,7 +982,7 @@ export default {
         });
     },
     handleDeleteBatch() {
-      let title = this.$t('test_track.case.batch_delete_completely_confirm', [this.$refs.table.selectIds.length]);
+      let title = this.$t('test_track.case.batch_delete_completely_confirm', [this.selectCounts]);
       this.$confirm(this.$t('test_track.case.batch_delete_tip'), title, {
           cancelButtonText: this.$t("commons.cancel"),
           confirmButtonText: this.$t("commons.delete"),