[MINOR] fix(docs) Correct the example of decommission interface (apac…

…he#1777)

### What changes were proposed in this pull request?
Correct the example of decommission interface

### Why are the changes needed?
The document content is incorrect.

### Does this PR introduce any user-facing change?
No.

### How was this patch tested?
No need.

docs/coordinator_guide.md

@@ -181,7 +181,7 @@ AccessQuotaChecker is a checker when the number of concurrent tasks submitted by
 ##### Example cURL
 
 > ```bash
->  curl -X POST -H "Content-Type: application/json" http://localhost:19998/api/server/decommission  -d '{"serverIds:": ["127.0.0.1:19999"]}'
+>  curl -X POST -H "Content-Type: application/json" http://localhost:19998/api/server/decommission  -d '{"serverIds": ["127.0.0.1-19999"]}'
 > ```
 </details>
 
@@ -219,7 +219,7 @@ AccessQuotaChecker is a checker when the number of concurrent tasks submitted by
 ##### Example cURL
 
 > ```bash
->  curl -X POST -H "Content-Type: application/json" http://localhost:19998/api/server/cancelDecommission  -d '{"serverIds:": ["127.0.0.1:19999"]}'
+>  curl -X POST -H "Content-Type: application/json" http://localhost:19998/api/server/cancelDecommission  -d '{"serverIds": ["127.0.0.1-19999"]}'
 > ```
 </details>