[skip e2e]Update milvus component name (#14685)

Signed-off-by: Nyanliang567 <yanliang.qiao@zilliz.com>

docs/design_docs/root_coordinator_recovery_on_power_failure.md

@@ -95,4 +95,4 @@
 
 ### 2.12 Timestamp of `dd operations`
 
-1. `RC` response is to set the timestamp of `dd operations`, create collection, create partition, drop collection, drop partition, and send this timestamp into `dml msgstream`.
+1. `RootCoord` response is to set the timestamp of `dd operations`, create collection, create partition, drop collection, drop partition, and send this timestamp into `dml msgstream`.