docs: Update sign.md

调整了 Demo 中 Seed 示例说明，修正文字描述

Author: Lucky-Qu

docs/develop/api-v2/dev-prepare/interface-framework/sign.md

@@ -35,7 +35,7 @@
 DEMO
 ```
 【输入】
-botSecret: naOC0ocQE3shWLAfffVLB1rhYPG7
+botSecret: naOC0ocQE3shWLAfffVLB1rhYPG7 
 seed: naOC0ocQE3shWLAfffVLB1rhYPG7naOC0ocQE3shWLAfffVLB1rhYPG7
 rand: naOC0ocQE3shWLAfffVLB1rhYPG7naOC
 【输出】