Reverting terraform to 0.12.7

Author: benj-fletch

go.mod

@@ -2,7 +2,7 @@ module github.com/terraform-providers/terraform-provider-github
 
 require (
 	github.com/google/go-github/v29 v29.0.3
-	github.com/hashicorp/terraform v0.12.20
+	github.com/hashicorp/terraform v0.12.7
 	github.com/kylelemons/godebug v1.1.0
 	github.com/terraform-providers/terraform-provider-tls v1.2.0
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d