Increment version to 2.20.0-SNAPSHOT

Signed-off-by: opensearch-ci-bot <[email protected]>

Author: opensearch-ci-bot

build.gradle

@@ -6,7 +6,7 @@
 buildscript {
 
     ext {
-        opensearch_version = System.getProperty("opensearch.version", "2.19.0-SNAPSHOT")
+        opensearch_version = System.getProperty("opensearch.version", "2.20.0-SNAPSHOT")
         isSnapshot = "true" == System.getProperty("build.snapshot", "true")
         buildVersionQualifier = System.getProperty("build.version_qualifier", "")