Fix endpoints for orgs custom roles (#2370)

Author: joshua-hancox

github/org_custom_roles.go github/orgs_custom_roles.gogithub/org_custom_roles.go renamed to github/orgs_custom_roles.go

@@ -29,7 +29,7 @@ type CustomRepoRoles struct {
 //
 // GitHub API docs: https://docs.github.com/en/rest/orgs/custom-roles
 func (s *OrganizationsService) ListCustomRepoRoles(ctx context.Context, org string) (*OrganizationCustomRepoRoles, *Response, error) {
-	u := fmt.Sprintf("organizations/%v/custom_roles", org)
+	u := fmt.Sprintf("orgs/%v/custom_roles", org)
 
 	req, err := s.client.NewRequest("GET", u, nil)
 	if err != nil {

github/org_custom_roles_test.go github/orgs_custom_roles_test.gogithub/org_custom_roles_test.go renamed to github/orgs_custom_roles_test.go

@@ -18,7 +18,7 @@ func TestOrganizationsService_ListCustomRepoRoles(t *testing.T) {
 	client, mux, _, teardown := setup()
 	defer teardown()
 
-	mux.HandleFunc("/organizations/o/custom_roles", func(w http.ResponseWriter, r *http.Request) {
+	mux.HandleFunc("/orgs/o/custom_roles", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "GET")
 		fmt.Fprint(w, `{"total_count": 1, "custom_roles": [{ "id": 1, "name": "Developer"}]}`)
 	})