Disable BWC for SLM retention backport

SLM retention was merged in elastic#46407 and will be backported in elastic#46506.
This disables BWC tests until both the backport and the version change
in elastic#46509 are merged.

build.gradle

@@ -176,8 +176,8 @@ task verifyVersions {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = true
-final String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
+boolean bwc_tests_enabled = false
+final String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/46509" /* 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")