[jdk21u] RFR: 8315863: [GHA] Update checkout action to use v4

Fri Sep 8 08:57:00 UTC 2023

Hi all,

This pull request contains a backport of commit [b74805d3](https://github.com/openjdk/jdk/commit/b74805d38395ca8be9308d882bf6b84e93714849) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Christian Stein on 7 Sep 2023 and was reviewed by Aleksey Shipilev.

Thanks!

-------------

Commit messages:
 - Backport b74805d38395ca8be9308d882bf6b84e93714849

Changes: https://git.openjdk.org/jdk21u/pull/146/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=146&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315863
  Stats: 7 lines in 7 files changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk21u/pull/146.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/146/head:pull/146

PR: https://git.openjdk.org/jdk21u/pull/146