actions/checkout v5 has come

Stream: lean4

[Asei Inoue]

lake new command would create the following workflow file:

name: Lean Action CI

on:
  push:
  pull_request:
  workflow_dispatch:

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4
      - uses: leanprover/lean-action@v1

but actions/checkout@v4 is a bit old. now latest is v5.

see: https://github.com/actions/checkout/tree/main

[Kim Morrison]

lean#10845