License header must be changed

[hendrikebbers]

Currently we have headers like this:

*-
 * ‌
 * Hedera Mirror Node
 * ​
 * Copyright (C) 2019 Hedera Hashgraph, LLC
 * ​
 * 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.
 * ‍
 */

We want to swith to SPDX license headers as described in this issue: hiero-ledger/tsc#64

[gsstoykov]

Same as my comment for #828

[rwalworth]

Is this not already done as a part of #823?

[gsstoykov]

It is done everywhere instead of the proto files which are still provided from services/mirror so we can close this I guess.