Fix the command to generate 'asc' file (#158)

diff --git a/_docs/08-release-manual.md b/_docs/08-release-manual.md
index 22c8210..347f741 100644
--- a/_docs/08-release-manual.md
+++ b/_docs/08-release-manual.md
@@ -110,8 +110,8 @@
 
 - sign files(generate `asc` file)
 ```
-gpg --clearsign rocketmq-all-x1.x2.x3-bin-release.zip
-gpg --clearsign rocketmq-all-x1.x2.x3-source-release.zip
+gpg -ab rocketmq-all-x1.x2.x3-bin-release.zip
+gpg -ab rocketmq-all-x1.x2.x3-source-release.zip
 ```
 - generate hash(generate `sha512` file)
 ```