remove duplicate checks in upgrade logic (#182)

* remove duplicate checks

* changelog

CHANGELOG.md

@@ -66,6 +66,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (07-tendermint) [\#182](https://github.com/cosmos/ibc-go/pull/182) Remove duplicate checks in upgrade logic.
 * (modules/core/04-channel) [\#7949](https://github.com/cosmos/cosmos-sdk/issues/7949) Standardized channel `Acknowledgement` moved to its own file. Codec registration redundancy removed.
 * (modules/core/04-channel) [\#144](https://github.com/cosmos/ibc-go/pull/144) Introduced a `packet_data_hex` attribute to emit the hex-encoded packet data in events. This allows for raw binary (proto-encoded message) to be sent over events and decoded correctly on relayer. Original `packet_data` is DEPRECATED. All relayers and IBC event consumers are encouraged to switch to `packet_data_hex` as soon as possible.
 * (modules/light-clients/07-tendermint) [\#125](https://github.com/cosmos/ibc-go/pull/125) Implement efficient iteration of consensus states and pruning of earliest expired consensus state on UpdateClient.

modules/core/02-client/types/proposal.go

@@ -111,10 +111,6 @@ func (up *UpgradeProposal) ValidateBasic() error {
 		return err
 	}
 
-	if up.Plan.Height <= 0 {
-		return sdkerrors.Wrap(ErrInvalidUpgradeProposal, "IBC chain upgrades must set a positive height")
-	}
-
 	if up.UpgradedClientState == nil {
 		return sdkerrors.Wrap(ErrInvalidUpgradeProposal, "upgraded client state cannot be nil")
 	}

modules/light-clients/07-tendermint/types/upgrade.go

@@ -71,10 +71,6 @@ func (cs ClientState) VerifyUpgradeAndUpdateState(
 		return nil, nil, sdkerrors.Wrap(err, "could not retrieve consensus state for lastHeight")
 	}
 
-	if cs.IsExpired(consState.Timestamp, ctx.BlockTime()) {
-		return nil, nil, sdkerrors.Wrap(clienttypes.ErrInvalidClient, "cannot upgrade an expired client")
-	}
-
 	// Verify client proof
 	bz, err := cdc.MarshalInterface(upgradedClient)
 	if err != nil {