Re-disable BWC tests after inadvertent re-enabling

These tests were disabled to facilitate backport of a PR which is not
yet complete. These tests were accidentally reenabled after a merge
conflict was resolved in the wrong direction. This commit addresses this
issue.

build.gradle

@@ -145,7 +145,7 @@ task verifyVersions {
  * after the backport of the backcompat code is complete.
  */
 allprojects {
-  ext.bwc_tests_enabled = true
+  ext.bwc_tests_enabled = false
 }
 
 task verifyBwcTestsEnabled {