Increment version to 3.8.0-SNAPSHOT

Signed-off-by: opensearch-ci-bot <opensearch-infra@amazon.com>

Author: opensearch-ci-bot

build.gradle

@@ -9,7 +9,7 @@ import java.nio.file.Paths
 
 buildscript {
     ext {
-        opensearch_version = System.getProperty("opensearch.version", "3.7.0-SNAPSHOT")
+        opensearch_version = System.getProperty("opensearch.version", "3.8.0-SNAPSHOT")
         buildVersionQualifier = System.getProperty("build.version_qualifier", "")
         isSnapshot = "true" == System.getProperty("build.snapshot", "true")
         version_tokens = opensearch_version.tokenize('-')