make governance::trigger_epoch an entry function

framework/libra-framework/sources/modified_source/diem_governance.move

@@ -574,7 +574,7 @@ module diem_framework::diem_governance {
     /// decides the epoch can change. Any error will just cause the
     /// user's transaction to abort, but the chain will continue.
     /// Whatever fix is needed can be done online with on-chain governance.
-    public fun trigger_epoch(_sig: &signer) acquires GovernanceResponsbility { // doesn't need a signer
+    public entry fun trigger_epoch(_sig: &signer) acquires GovernanceResponsbility { // doesn't need a signer
       let framework_signer = get_signer(@0x1);
       let _ = epoch_boundary::can_trigger(); // will abort if false
       epoch_boundary::trigger_epoch(&framework_signer);