docker-build: Update actions/checkout to v3
For hacktoberfest 2022 :)
_The documentation is not available anymore as the PR was closed or merged._<|||||>Thanks for your PR @Sushrut1101! I'll ping Yih-Dar @ydshieh for review but he's off for the week; he'll review when he's back! Thanks :)<|||||>> Thanks for your PR @Sushrut1101! I'll ping Yih-Dar @ydshieh for review but he's off for the week; he'll review when he's back! Thanks :)



> Actually checked and it's fine for me; thanks for your PR @Sushrut1101!

You're welcome! 👍😃