update intro md docker tag

Author: chivehao

docs/intro.md

@@ -46,7 +46,7 @@ docker run \
   --name ikaros \
   -p 9999:9999 \
   -v ~/.ikaros:/root/.ikaros \
-  ikarosrun/ikaros:v0.20.9 \
+  ikarosrun/ikaros:v0.21.0 \
   --ikaros.security.initializer.master-username=tomoki \
   --ikaros.security.initializer.master-password=tomoki
 ```

versioned_docs/version-0.20/intro.md

@@ -46,7 +46,7 @@ docker run \
   --name ikaros \
   -p 9999:9999 \
   -v ~/.ikaros:/root/.ikaros \
-  ikarosrun/ikaros:v0.20.9 \
+  ikarosrun/ikaros:v0.20.11 \
   --ikaros.security.initializer.master-username=tomoki \
   --ikaros.security.initializer.master-password=tomoki
 ```

versioned_docs/version-0.21/intro.md

@@ -46,7 +46,7 @@ docker run \
   --name ikaros \
   -p 9999:9999 \
   -v ~/.ikaros:/root/.ikaros \
-  ikarosrun/ikaros:v0.20.9 \
+  ikarosrun/ikaros:v0.21.0 \
   --ikaros.security.initializer.master-username=tomoki \
   --ikaros.security.initializer.master-password=tomoki
 ```