Turn off next major tests for private modules for now

private-modules-overrides.yml

 variables:
   OPT_IN_TEST_NEXT_MINOR: 1
-  OPT_IN_TEST_NEXT_MAJOR: 1
+  OPT_IN_TEST_NEXT_MAJOR: 0
   RUN_JOB_UPGRADE_STATUS: 1
 
 .provide-info-yml-if-needed: &provide-info-yml-if-needed