Adjust CWL Sink Threshold to allow minimal 10 second flush interval (#6242)

**What?**

This commit updates CWL sink minimal allowed flush interval from 60s
to 10s.

**Why?**

CWL is a high TPS dataplane service with small batch of events. It is
reasonable to allow shorter flush interval to improve the ingestion
latency

Signed-off-by: Wenjie Yao <wjyao@amazon.com>
Co-authored-by: Wenjie Yao <wjyao@amazon.com>

Author: wjyao0316

data-prepper-plugins/cloudwatch-logs/src/main/java/org/opensearch/dataprepper/plugins/sink/cloudwatch_logs/config/ThresholdConfig.java

@@ -44,7 +44,7 @@ public class ThresholdConfig {
     private ByteCount maxRequestSize = DEFAULT_MAX_REQUEST_SIZE;
 
     @JsonProperty("flush_interval")
-    @DurationMin(seconds = 60)
+    @DurationMin(seconds = 10)
     @DurationMax(seconds = 3600)
     private Duration flushInterval = Duration.ofSeconds(DEFAULT_FLUSH_INTERVAL);