authz: Clean up acl endpoints and dashboard guardian (#73746)

* RBAC: remove unnessisary guardian construction and update tests

* RBAC: remove usage of guardian in UpdateFolderPermissions and refactor test

* RBAC: remove usage of guardian in update and get permissions for dashboards

pkg/api/utils.go

@@ -1,7 +1,6 @@
 package api
 
 import (
-	"encoding/json"
 	"net/mail"
 
 	"github.com/grafana/grafana/pkg/middleware/cookies"
@@ -21,12 +20,6 @@ func (hs *HTTPServer) GetRedirectURL(c *contextmodel.ReqContext) string {
 	return redirectURL
 }
 
-func jsonMap(data []byte) (map[string]string, error) {
-	jsonMap := make(map[string]string)
-	err := json.Unmarshal(data, &jsonMap)
-	return jsonMap, err
-}
-
 func ValidateAndNormalizeEmail(email string) (string, error) {
 	if email == "" {
 		return "", nil