Update dependencies (#325)

Signed-off-by: Julien Pivotto <[email protected]>

go.mod

@@ -1,26 +1,9 @@
 module github.com/terraform-providers/terraform-provider-gitlab
 
 require (
-	cloud.google.com/go/storage v1.6.0 // indirect
-	github.com/aws/aws-sdk-go v1.29.30 // indirect
-	github.com/golang/protobuf v1.4.0 // indirect
-	github.com/hashicorp/go-hclog v0.12.1 // indirect
-	github.com/hashicorp/go-retryablehttp v0.6.6 // indirect
-	github.com/hashicorp/hcl v1.0.0 // indirect
-	github.com/hashicorp/hcl/v2 v2.3.0 // indirect
-	github.com/hashicorp/terraform-config-inspect v0.0.0-20200210163047-f7d8399e1194 // indirect
-	github.com/hashicorp/terraform-plugin-sdk v1.8.0
-	github.com/hashicorp/terraform-svchost v0.0.0-20191119180714-d2e4933b9136 // indirect
-	github.com/hashicorp/yamux v0.0.0-20190923154419-df201c70410d // indirect
+	github.com/hashicorp/terraform-plugin-sdk v1.13.1
 	github.com/mitchellh/hashstructure v1.0.0
-	github.com/posener/complete v1.2.3 // indirect
-	github.com/ulikunitz/xz v0.5.7 // indirect
-	github.com/vmihailenco/msgpack v4.0.4+incompatible // indirect
 	github.com/xanzy/go-gitlab v0.32.1
-	golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59 // indirect
-	golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0 // indirect
-	golang.org/x/time v0.0.0-20200416051211-89c76fbcd5d1 // indirect
-	google.golang.org/appengine v1.6.6 // indirect
 )
 
 go 1.14