build: go 1.24

We were running behind and there were quite some deprecations to update.
This was mostly in the upstream copy/pasta package but seems quite
minimal.

vendor/google.golang.org/grpc/internal/grpcsync/oncefunc.go

@@ -1,32 +0,0 @@
-/*
- *
- * Copyright 2022 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-package grpcsync
-
-import (
-	"sync"
-)
-
-// OnceFunc returns a function wrapping f which ensures f is only executed
-// once even if the returned function is executed multiple times.
-func OnceFunc(f func()) func() {
-	var once sync.Once
-	return func() {
-		once.Do(f)
-	}
-}