GitHub allows you to delete each GitHub Action run separately. Removing all of them at once is not possible in UI. As a workaround, the GitHub API can be used to automate the workflow deletion.
This can be necessary, if you want to make you private repo, publicly available but your Action executions have sensitive data stored in logs.
You can use the GitHub CLI to make API calls.
# 1. Export organization and repository name
export OWNER=mszostok
export REPO=aaas
# 2. List workflows
gh api -X GET /repos/$OWNER/$REPO/actions/workflows | jq '.workflows[] | .name,.id'
# 3. Copy the ID of the workflow you want to clear and set it
export WORKFLOW_ID=12478829
# 4. [SANITY CHECK] list runs that will be removed
gh api -X GET /repos/$OWNER/$REPO/actions/workflows/$WORKFLOW_ID/runs --paginate | jq '.workflow_runs[] | .id'
# 5. Delete all runs for a given workflow
gh api -X GET /repos/$OWNER/$REPO/actions/workflows/$WORKFLOW_ID/runs --paginate | jq '.workflow_runs[] | .id' | xargs -I{} gh api -X DELETE /repos/$OWNER/$REPO/actions/runs/{} --silent