Update dependencies

This commit updates the following dependencies:

1. terraform-plugin-sdk to 2.6.1
2. golang.org/x/crypto to v0.0.0-20210616213533-5ff15b29337e

go.mod

@@ -3,10 +3,10 @@ module github.com/hetznercloud/terraform-provider-hcloud
 require (
 	github.com/hashicorp/go-cty v1.4.1-0.20200414143053-d3edf31b6320
 	github.com/hashicorp/go-multierror v1.1.1
-	github.com/hashicorp/terraform-plugin-sdk/v2 v2.5.0
+	github.com/hashicorp/terraform-plugin-sdk/v2 v2.6.1
 	github.com/hetznercloud/hcloud-go v1.27.0
 	github.com/stretchr/testify v1.7.0
-	golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2
+	golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e
 )
 
 go 1.16