fixBug('#6172') Dag node name value judgment error (#6175)

Co-authored-by: Nxiangcaibiao <caibiao.xiang@sinocare.com>

dolphinscheduler-ui/src/js/conf/home/pages/dag/_source/formModel/formModel.vue

@@ -695,7 +695,7 @@
         }
         // Name repeat depends on dom backfill dependent store
         const tasks = this.store.state.dag.tasks
-        const task = tasks.find((t) => t.name === 'this.name')
+        const task = tasks.find((t) => t.name === this.name)
         if (task) {
           this.$message.warning(`${i18n.$t('Name already exists')}`)
           return false