Update demo.yml (#1210)

Signed-off-by: link <a624669980@163.com>

.github/workflows/demo.yml

@@ -34,7 +34,7 @@ jobs:
       - name: Get old instance and snapshot name, create new instance name
         run: | 
           echo "OLD_INSTANCE_SNAPSHOT_NAME=$(aws lightsail get-instance-snapshots | grep '"name": "updateto_to_0.4.4-1684926517' | sed 's/ //g' | sed 's/"//g' | sed 's/,//g' | sed 's/name://g')" >> $GITHUB_ENV
-          echo "OLD_INSTANCE_NAME=$(aws lightsail get-instances | grep '"name": "CasaOS-Demo-[0-9]' | sed 's/ //g' | sed 's/"//g' | sed 's/,//g' | sed 's/name://g')" >> $GITHUB_ENV
+          echo "OLD_INSTANCE_NAME=$(aws lightsail get-instances | grep '"name": "CasaOS-Demo-[0-9]' | head -n 1 | sed 's/ //g' | sed 's/"//g' | sed 's/,//g' | sed 's/name://g')" >> $GITHUB_ENV
           echo "NEW_INSTANCE_NAME= CasaOS-Demo-$(date +%s)" >> $GITHUB_ENV
           
       - name: Create instances from snapshot