Re-enable bwc tests after #27881 was backported

build.gradle

@@ -139,8 +139,7 @@ task verifyVersions {
  * after the backport of the backcompat code is complete.
  */
 allprojects {
-  // TODO: re-enable after https://github.com/elastic/elasticsearch/pull/27881 is backported
-  ext.bwc_tests_enabled = false
+  ext.bwc_tests_enabled = true
 }
 
 task verifyBwcTestsEnabled {