docs: update hemonc instructions in readme (#397)

* Add link to harvard dataverse website

README.md

@@ -79,7 +79,7 @@ You must set the `UMLS_API_KEY` environment variable to your API key. This can b
 export UMLS_API_KEY=12345-6789-abcdefg-hijklmnop  # make sure to replace with your key!
 ```
 
-HemOnc.org data requires a Harvard Dataverse API key. After creating a user account on the Harvard Dataverse website, you can follow [these instructions](https://guides.dataverse.org/en/latest/user/account.html) to generate a key. Once you have a key, set the following environment variable:
+HemOnc.org data requires a Harvard Dataverse API token. You must create a user account on the [Harvard Dataverse website](https://dataverse.harvard.edu/), you can follow [these instructions](https://guides.dataverse.org/en/latest/user/account.html) to create an account and generate an API token. Once you have an API token, set the following environment variable:
 
 ```shell script
 export DATAVERSE_API_KEY=12345-6789-abcdefgh-hijklmnop  # make sure to replace with your key!