chore: transfer authz nits (backport #3586) (#3589)

* chore: optimise transfer authz to consume less gas for unbounded spend limits (#3586)

(cherry picked from commit f6e8f03)

# Conflicts:
#	modules/apps/transfer/types/transfer_authorization.go

* resolve conflicts

---------

Co-authored-by: Damian Nolan <damiannolan@gmail.com>

modules/apps/transfer/types/transfer_authorization.go

@@ -48,7 +48,7 @@ func (a TransferAuthorization) Accept(ctx sdk.Context, msg sdk.Msg) (authz.Accep
 
 		// If the spend limit is set to the MaxUint256 sentinel value, do not subtract the amount from the spend limit.
 		if allocation.SpendLimit.AmountOf(msgTransfer.Token.Denom).Equal(UnboundedSpendLimit()) {
-			return authz.AcceptResponse{Accept: true, Delete: false, Updated: &a}, nil
+			return authz.AcceptResponse{Accept: true, Delete: false, Updated: nil}, nil
 		}
 
 		limitLeft, isNegative := allocation.SpendLimit.SafeSub(msgTransfer.Token)

modules/apps/transfer/types/transfer_authorization_test.go

@@ -93,11 +93,9 @@ func (suite *TypesTestSuite) TestTransferAuthorizationAccept() {
 			func(res authz.AcceptResponse, err error) {
 				suite.Require().NoError(err)
 
-				updatedTransferAuthz, ok := res.Updated.(*types.TransferAuthorization)
-				suite.Require().True(ok)
-
-				remainder := updatedTransferAuthz.Allocations[0].SpendLimit.AmountOf(sdk.DefaultBondDenom)
-				suite.Require().True(types.UnboundedSpendLimit().Equal(remainder))
+				suite.Require().True(res.Accept)
+				suite.Require().False(res.Delete)
+				suite.Require().Nil(res.Updated)
 			},
 		},
 		{