Temporarily disable BWC for retention lease stats (#38049)

This commit temporarily disables BWC testing while backporting a change
to expose retention leases in stats.

build.gradle

@@ -159,8 +159,8 @@ task verifyVersions {
  * the enabled state of every bwc task. It should be set back to true
  * after the backport of the backcompat code is complete.
  */
-final boolean bwc_tests_enabled = true
-final String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
+final boolean bwc_tests_enabled = false
+final String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/37991" /* place a PR link here when committing bwc changes */
 if (bwc_tests_enabled == false) {
   if (bwc_tests_disabled_issue.isEmpty()) {
     throw new GradleException("bwc_tests_disabled_issue must be set when bwc_tests_enabled == false")