remove update command

Author: Oreoxmt

dm/dm-manage-source.md

@@ -32,7 +32,7 @@ help operate-source
 ```
 
 ```
-`create`/`update`/`stop`/`show` upstream MySQL/MariaDB source.
+`create`/`stop`/`show` upstream MySQL/MariaDB source.
 
 Usage:
   dmctl operate-source <operate-type> [config-file ...] [--print-sample-config] [flags]
@@ -47,11 +47,9 @@ Global Flags:
 
 ### Flags description
 
-+ `create`: Creates one or more upstream database source(s). When creating multiple data sources fails, DM rolls back to the state where the command was not executed.
++ `create`: Creates one or more upstream database sources. When creating multiple data sources fails, DM rolls back to the state where the command was not executed.
 
-+ `update`: Updates an upstream database source.
-
-+ `stop`: Stops one or more upstream database source(s). When stopping multiple data sources fails, some data sources might be stopped.
++ `stop`: Stops one or more upstream database sources. When stopping multiple data sources fails, some data sources might be stopped.
 
 + `show`: Shows the added data source and the corresponding DM-worker.
 

dm/dmctl-introduction.md

@@ -49,7 +49,7 @@ Available Commands:
   offline-member  Offlines member which has been closed.
   operate-leader  `evict`/`cancel-evict` the leader.
   operate-schema  `get`/`set`/`remove` the schema for an upstream table.
-  operate-source  `create`/`update`/`stop`/`show` upstream MySQL/MariaDB source.
+  operate-source  `create`/`stop`/`show` upstream MySQL/MariaDB source.
   pause-relay     Pauses DM-worker's relay unit.
   pause-task      Pauses a specified running task.
   purge-relay     Purges relay log files of the DM-worker according to the specified filename.