Request: upgrade actions/checkout

[nard-tech]

Maybe related to #859

Now https://github.com/actions/checkout V2 is released, so please upgrade.

As I reported on #859, I tried to fix broken CI in #858. At the same time I tried to fix this issue (cf. 11863b1), but I could not fix entire problems due to other complicated reasons.

So I did not upgrade actions/checkout by myself.

Codes

annotate_models/.github/workflows/ci.yml

Lines 19 to 21 in 70aba78

	steps:
	- name: Checkout
	uses: actions/checkout@v1

Version

• annotate version: 3.1.1
• rails version: 5.2.4.1, 6.0.2.1
• ruby version: 2.4, 2.5, 2.6