Add additional upgrade step to README

README.md

@@ -9,7 +9,8 @@ This is a lightweight fork of CosmosSDK. The current version of the forked code
 3. After merging, update the `v4` repository's `go.mod`, and `go.sum` files with your merged `$COMMIT_HASH`.
 4. (In `dydxprotocol/v4`) `go mod edit -replace github.com/cosmos/cosmos-sdk=github.com/dydxprotocol/cosmos-sdk@$COMMIT_HASH`
 5. (In `dydxprotocol/v4`) `go mod tidy`
-6. Open a PR in `dydxprotocol/v4` to bump the version of the fork.
+6. (In `dydxprotocol/v4`) update package references in `mocks/Makefile`. See [here](https://github.com/dydxprotocol/v4/pull/848) for an example.
+7. Open a PR in `dydxprotocol/v4` to bump the version of the fork.
 
 ## Fork maintenance