[MINOR] docs: modify the default value of `rss.coordinator.select.partition.strategy` in docs (#1692)

### What changes were proposed in this pull request?
Modify the default value of rss.coordinator.select.partition.strategy in docs.

### Why are the changes needed?
The current document is wrong.

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

### How was this patch tested?
No need
diff --git a/docs/client_guide/spark_client_guide.md b/docs/client_guide/spark_client_guide.md
index 2f2dcbb..80783f7 100644
--- a/docs/client_guide/spark_client_guide.md
+++ b/docs/client_guide/spark_client_guide.md
@@ -62,7 +62,7 @@
 
     It can be enabled by the following config
       ```bash
-        # Default value is ROUND, it will poll to allocate partitions to ShuffleServer
+        # Another value is ROUND, it will poll to allocate partitions to ShuffleServer
         rss.coordinator.select.partition.strategy CONTINUOUS
         
         # Default value is 1.0, used to estimate task concurrency, how likely is this part of the resource between spark.dynamicAllocation.minExecutors and spark.dynamicAllocation.maxExecutors to be allocated
diff --git a/docs/coordinator_guide.md b/docs/coordinator_guide.md
index ca31707..b33bbba 100644
--- a/docs/coordinator_guide.md
+++ b/docs/coordinator_guide.md
@@ -101,7 +101,7 @@
 |rss.coordinator.remote.storage.io.sample.access.times|3| The number of times to read and write HADOOP FS files                                                                                                                                                                                                                    |
 |rss.coordinator.startup-silent-period.enabled|false| Enable the startup-silent-period to reject the assignment requests for avoiding partial assignments. To avoid service interruption, this mechanism is disabled by default. Especially it's recommended to use in coordinator HA mode when restarting single coordinator. |
 |rss.coordinator.startup-silent-period.duration|20000| The waiting duration(ms) when conf of rss.coordinator.startup-silent-period.enabled is enabled.                                                                                                                                                                          |
-|rss.coordinator.select.partition.strategy|ROUND| There are two strategies for selecting partitions: ROUND and CONTINUOUS. ROUND will poll to allocate partitions to ShuffleServer, and CONTINUOUS will try to allocate consecutive partitions to ShuffleServer, this feature can improve performance in AQE scenarios.    |
+|rss.coordinator.select.partition.strategy|CONTINUOUS| There are two strategies for selecting partitions: ROUND and CONTINUOUS. ROUND will poll to allocate partitions to ShuffleServer, and CONTINUOUS will try to allocate consecutive partitions to ShuffleServer, this feature can improve performance in AQE scenarios.    |
 |rss.metrics.reporter.class|-| The class of metrics reporter.                                                                                                                                                                                                                                           |
 |rss.reconfigure.interval.sec|5| Reconfigure check interval.                                                                                                                                                                                                                                              |