A fee allowance grant will be created with the MsgGrantAllowance message.
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/proto/cosmos/feegrant/v1beta1/tx.proto#L23-L36
An allowed grant fee allowance can be removed with the MsgRevokeAllowance message.
+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/proto/cosmos/feegrant/v1beta1/tx.proto#L41-L50