Cannot set concurrency

[Bilge]

Describe the bug
According to action.yml, we can set the concurrency. However, setting this parameter appears to have no effect.

action-docker-layer-caching/action.yml

Lines 17 to 20 in cc3f382

	concurrency:
	description: The number of concurrency when restoring and saving layers
	required: true
	default: '4'

To Reproduce
Steps to reproduce the behavior:

      - uses: satackey/action-docker-layer-caching@v0.0.11
        with:
          concurrency: 2

Expected behavior
concurrency: 2 should appear in the build output.

Debug logs

Run satackey/action-docker-layer-caching@v0.0.11
with:
key: docker-layer-caching-CI-{hash}
restore-keys: docker-layer-caching-CI-
concurrency: 4
skip-save: false

Runner Environment (please complete the following information):

• OS: ubuntu-latest
• Action version: v0.0.11