Migrate set-output to $GITHUB_OUTPUT

[tanakakc]

https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

[znz]

test failed but I think it does not relate this change.

https://github.com/ruby/find/actions/runs/3973315966/jobs/6811920836#step:4:6

ERROR:  Error installing bundler:
	The last version of bundler (>= 0) to support your Ruby & RubyGems was 2.3.2[6](https://github.com/ruby/find/actions/runs/3973315966/jobs/6811920836#step:4:7). Try installing it with `gem install bundler -v 2.3.26`
	bundler requires Ruby version >= 2.6.0. The current ruby version is 2.5.0.
Error: Process completed with exit code 1.

[hsbt]

@znz I fixed build failure with #9