Revert "Add GENRULE_SANDBOXING=false to non-sandboxed builds"

Revert submission 2782270-genrule_sandboxing_by_default

Reason for revert: Potential culprit for b/305851039 and many other build breakages - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Reverted changes: /q/submissionid:2782270-genrule_sandboxing_by_default

Change-Id: I7b47a92e1b315add65c8018500d9ffbd58f8f1dd