Increment version to 3.4.0-SNAPSHOT (#4279)

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

Author: opensearch-trigger-bot[bot]

build.gradle

@@ -11,7 +11,7 @@ buildscript {
     ext {
         opensearch_group = "org.opensearch"
         isSnapshot = "true" == System.getProperty("build.snapshot", "true")
-        opensearch_version = System.getProperty("opensearch.version", "3.3.0-SNAPSHOT")
+        opensearch_version = System.getProperty("opensearch.version", "3.4.0-SNAPSHOT")
         buildVersionQualifier = System.getProperty("build.version_qualifier", "")
         asm_version = "9.7"