Revert "Bump bwc version (opensearch-project#1876)"

This reverts commit 501392e.

Author: MitchellGale

integ-test/build.gradle

@@ -38,7 +38,7 @@ apply plugin: 'java'
 apply plugin: 'io.freefair.lombok'
 apply plugin: 'com.wiredforcode.spawn'
 
-String baseVersion = "2.10.0"
+String baseVersion = "2.9.0"
 String bwcVersion = baseVersion + ".0";
 String baseName = "sqlBwcCluster"
 String bwcFilePath = "src/test/resources/bwc/"