Reenable BWC tests after disabling for backport

This commit reenables the BWC tests after they were disabled for
backporting the change to track global checkpoints of shard copies on
the primary.

Relates #26666

build.gradle

@@ -175,7 +175,7 @@ task verifyVersions {
  * after the backport of the backcompat code is complete.
  */
 allprojects {
-  ext.bwc_tests_enabled = false
+  ext.bwc_tests_enabled = true
 }
 
 task verifyBwcTestsEnabled {