fix broken link (hashicorp#4329)

website/source/docs/secrets/gcp/index.html.md

@@ -77,7 +77,7 @@ Once the secrets engine has been set up, you can generate two types of secrets i
     [IAM service account keys](https://cloud.google.com/iam/docs/service-accounts#service_account_keys).
 
 
-Each secret is associated with a [Vault lease](docs/concepts/lease.html) that
+Each secret is associated with a [Vault lease](/docs/concepts/lease.html) that
 can be revoked and possibly renewed (see lease docs for how to do so). On revoking
 a lease, the secret is no longer guaranteed to work.
 
@@ -587,4 +587,4 @@ you run into. It could be that the API is a non-standard form or we need to re-g
 
 ## API
 The GCP secrets engine has a full HTTP API. Please see the [GCP secrets engine API docs](/api/secret/gcp/index.html) 
-for more details.
+for more details.