Revert "Increment version to 2.19.5-SNAPSHOT (#4985) (#5077)"

This reverts commit 40679f5.

Signed-off-by: Lantao Jin <ltjin@amazon.com>

Author: LantaoJin

build.gradle

@@ -6,7 +6,7 @@
 
 buildscript {
     ext {
-        opensearch_version = System.getProperty("opensearch.version", "2.19.5-SNAPSHOT")
+        opensearch_version = System.getProperty("opensearch.version", "2.19.4-SNAPSHOT")
         isSnapshot = "true" == System.getProperty("build.snapshot", "true")
         buildVersionQualifier = System.getProperty("build.version_qualifier", "")
         version_tokens = opensearch_version.tokenize('-')