Revert "Add system scope v3 token support"

This reverts commit c59b3bd4e686b0bd7925623ffe792694d4bff1f5.

Reason for revert: doesn't work as expected

Change-Id: I7f650a503c7ab5f55776a7a8c44e868c60dd923e
diff --git a/auth_options.go b/auth_options.go
index eaf4b68..eabf182 100644
--- a/auth_options.go
+++ b/auth_options.go
@@ -59,8 +59,6 @@
 	// TokenID allows users to authenticate (possibly as another user) with an
 	// authentication token ID.
 	TokenID string `json:"-"`
-
-	SystemScope bool `json:"-"`
 }
 
 // ToTokenV2CreateMap allows AuthOptions to satisfy the AuthOptionsBuilder
@@ -261,14 +259,6 @@
 		}
 	}
 
-	if opts.SystemScope {
-		return map[string]interface{}{
-			"system": map[string]interface{}{
-				"all": true,
-			},
-		}, nil
-	}
-
 	if scope.ProjectName != "" {
 		// ProjectName provided: either DomainID or DomainName must also be supplied.
 		// ProjectID may not be supplied.